I've tried the LBT Magnum 5.1's, Turtle Beach HPA2 5.1's for true 5.1 headsets, and the plantronics 777 emulated, and a few others that aren't worth mentioning from Razor (lower quality HPA2), etc. What I found out of those was the HPA2 was the clear winner, bang for the buck, a lotta bass, not much for soundstage though. What I thought was a decent soundstage was wiped out by a larger and better set of $33 headphones unamped compared to the amplified 5.1 headphones. Not saying the HPA2's are crap, they're quite the contrary, but overall, now I realize my money could've been much better spent elsewhere and I could've saved a lot and filled my fuel tank twice without regretting any sound output from my PC wether it be from games, movies or music...simple as that.
The amp on the HPA2 is nice, but in all honesty it is quite weak and well, not uber quality. If it were, the headset would cost much, much more than it currently does. Though it's the easiest way to 5.1, and has 4 speakers per cup, the 30mm sub doesn't match the single driver of the 50mm JVC HA-RX700...argue all you want, until you try a set, all you can do is argue. It might take a tad more EQ and a little bass boost, but in the end, it can provide a lot more than any gaming headset I've heard in the sub-$100 range.
Here's some things I've learned along the way, soundstage is extremely important...though if you're a basshead, which seems to mean, do you like bass or don'tcha? If you don't mind a lack of hit, but a presence of sound, then get something like the AudioTechnica AD-700/AD-900 as it seems on many places they're amazing for gaming due to a vast soundstage, great mids/hi's, but bass-wise due to the open backed nature, lack a lot of bass due to sound leakage...which also means sounds externally of the headphones will leak in more easily.
Now if you're like me, I don't generally consider myself a heavy basshead, but none-the-less I love the impact as much as the sound ouptut, and sometimes I want all I can handle...I'm a basshead. It's simple as that, a decent closed-back headphone is where it's at. Though it can vary from headphone part number and brand, there are many that will suit the needs of many. A place like head-fi.org might over-exagerate small discrepencies, so start off cheaper. The JVC HA-RX700's are the perfect fit for that bill, a great closed-back for very cheap that need little to no amplification for a pretty solid sound ouput. Again, I'll mention I've spent YEARS on the Turtle Beach HPA2's, I know what both versions are capable of (version 1 = wall plug powered, version 2 = usb plug powered + more bass). The conclusion I've come to is it's much cheaper and much, much better overall to have a set of headphones plus a decent mic (like the HPA2 mic:
http://www.turtlebeach.com/products/efhpa2/replacementparts.aspx ).
If you have a decent sound card that is, I have tried thise on the stock ALC885 and AD2000 MB sound on my GB P35-DS3L and Asus P5Q-Deluxe boards, the X-Fi Xtreme Music stomped them both into the ground without any chance in hell of either being even close to similar quality imho. The seperation, overall stage, freqency, adjustability, etc was just so much better and clearer on the x-fi it wasn't funny. Then I go from the X-Fi Xtreme Music to the newer Auzen X-Fi Forte, with the dedicated headphone amplifier, and......wow. I can't believe the difference, the seperation is so much better, the mids and hi's are more easily found with little to no EQ balance compared to the older x-fi, the bass is also more easily found with no boost and some EQ adjustment, it's great.
Not dogging 5.1 headsets, but at this rate, they need to re-think a few things, like cup size and placement. The LTB Magnums had a larger cup, smaller center and rear drivers, and did have better placement, but overall sounded very isolated and muffled, crap quality and randome cutouts lead to a worthless headset along with a very crappy mic (no boom, just a mic built into the lh ear cup, it would pick up the neighbors random sbd fart quite easily...was really, really bad for TS, etc).
I've tried a few different 5.1 true headsets and emulated 5.1/7.1's, what impressed me most was the emulated version's ability to sound better...not necessarily quality-wise, but actual placement and distance wise. That can be HUGE in FPS games.
Now I have tried the HPA2's in 2.1 and headphone mode, many might not be aware, but in that case the amp still drives the front and sub channels, it's part of their design, but even as an open back headphone, they sounded so isolated and closed that distance is almost non-existant in comparison to a cheap set of JVC headphones...and that's no joke. Not that I'm poking the bear, just pointing out what I noticed with my ears, money, dedication and time. If I believe in it, I share it here on TPU, if you don't believe it, look at my history of posts. I've posted some links as I was in the same position as the OP a few weeks ago (see on page 2 iirc, I posted a link to a thread titled "Considering a new headset".). I loved my HPA2's, believed that they were by far the best I could do under $100 in 5.1 or less...boy was I wrong...by a lot, and then some. There's no competition, the JVC HA-RX700 + 9ft of 3.5mm cable extension for mic + 2 zip small zip ties + TB HPA2 Non-Lock Mic > Turtle Beach HPA2. Even w/o any settings messed with I enjoy the sound extracted from the JVC's over the HPA2's. Sure the amp is easy to tune, and it's really very, very nice having an external master volume control...now I realize it's not a massive REQUIREMENT. I had to learn this from experience though and almost spent $80 for the Creative X-Fi Titanium FP...which I still may get as the Auzen has the dedicated amp for front and rear and has a higher db output for the FP channels. But for now I'm so happy I could care less...my fiance took over my HPA2's and instead of spending $80+ on another set, I spent less than $45 total for the JVC's, some 3.5mm cable and an HPA2 mic.
The trick is to go to control panel, then Sound, set the primary sound ouptut to 5.1 channels. Then set the sound card (X-FI at least) to headphone or 2.1 mode ( I prefer headhpone mode), and cmms-3d. I did this on the HPA2 and noticed that in just headphone mode I had similar placement to 5.1, not quite as good though. On the JVC's, it opened up a whole new world..look at my 2nd or 3rd post in this thread, the cups on the JVC's are easily twice as large as the HPA2 cups...with 3 less speakers per cup, plus a larger speaker than any of the ones provided in the turtle beaches and from the sound ouptut, seems much better quality and thought. I have less ound leakage in and out, so I can listen at lower volumes without hinder, issues, annoyances, so less ear-drum damage. Plus when configured like I stated above for game mode, it equals very simlar placement of sounds with much better distance...I can actually tell when I have a more serious threat that needs attended to now...something the HPA2's only hinted at, but due to design, size and quality was much more limited. I love the HPA2's still, and if you must, must, must have a cheap and true 5.1 headset that is the way to go...if you can afford more, play much, much more for the A40's, if not, have a decent sound card with either X-Fi CMMS3D or Dolby Headphone and a decent set of cans. Not saying my $33 set of JVC's are even decent, but compared to the HPA2's in music and games, they're easily worth much more. I'm not an audiophile, but I'm a fan of decent sound and good value. That's where my recommendations come from and why I post them, I look forward to helping others achieve something as good or better than I have for the same or less on the fundage side while still being able to be very content with their purchase. There's a wide world for sound out there, and the HPA2's have made a good dent, but in my opinion vs. an X-Fi and JVC HA-RX700, that candle is easily blown out and forgotten about...this coming from a guy used to years of 5.1 headsets with an X-Fi. But also remember, it comes down to the listeners ears and what they expect, listen for and want to hear, what I hear may not be what you want to hear, what Frederik S or Anisotonic wants to hear might not be what you want to hear, in the end that's what sucks in this arena, it can be so different and variated it's almost rediculous. Though I can easily vouch a decent sound card, amped or not will treat you better than onboard for gaming, music and movies, the headphone vs headset movement will continue on here and away. I used to vouch that headsets had a strong value, and they do...for those that are either too lazy or don't wanna deal with adding a mic, go for it...but at the cost of sound, sound stage and sound quality in general...unless you pay much, much, much more...is it really worth the hassle of a headphone + mic (even the clip-on Zalman mic)? Most that have gone that route after headsets will say yes without hesitation. You get more for your buck, something that will last longer, get the job done better, and be something you might be more content with for a while longer or even just flat out last longer. Headsets are here to stay, but headphones are going nowhere in the gaming industry...all I can see truly happening is more good headphones being converted to headsets...but at what cost? Will it be worth it over a couple of zip ties to you? If you're not picky on sound, Plantronics, Logitech, Creative, etc will do very well and even put out great sound and have some solid performers...but at the price those solld performers retail at, so much more can be found for if you go for it a different way, imho it's worth it.