I like to keep RAID simple, or avoid it altogether. Unless you're going to buy an expensive hardware RAID card, which I don't think you are, then you're talking about software RAID, which takes a toll on the CPU.
Raid10 is the obvious for your requirements - 4x2TB striped and mirrored, so you have 4TB usable with redundancy. Depending on whether the RAID10 you get is RAID0+1 or RAID1+0, you can lose any 1 drive, and maybe
2 under specific circumstances. 2TB drives because they're a lot cheaper than 3TB. RAID 10 will use a decent bit of CPU though.
If you can get away with just 3TB of usable storage, I'd be very tempted to get 2x3TB and just mirror it. Nice and simple. Not so much to go wrong.
You can go down the whole RAID5 kind of route with parity, essentially having 2x2TB and 1x 1TB parity - I personally wouldn't bother. Just stick to mirror, and only stripe them too if necessary. Keep It Simple S...you know the rest.
What can still go wrong, even with all this mirrored redundancy, is that the machine itself is tampered with/damaged/stolen/etc. I'd be tempted to make sure all this doesn't go to waste by setting up an online stream to an offsite box, where you store the data again. Hopefully, the CCTV software has this kind of facility already.
As for the drives themselves, if you go for the expensive 3TBs you haven't much choice, there are about 3 options. Hitachi seems to state more start/stop cycles than WD, and they're faster, but they cost more. WD's 5.4k drives are pretty energy efficient and cheaper. Maybe go for those? - you don't need additional speed I don't think. All 3tb are AF (4k).
For 2TB, I'd personally go for Samsung as 1st pref, with Hitachi or WD following. As stated earlier, WD's 5.4k range may do you well. But... everybody will give you differing recommendations here, it's down to personal preference at the end of the day.
As for a PSU, again, this is personal preference. The site HardwareSecrets does fantastic PSU reviews; you'd be well advised to check any candidate PSUs there before purchasing. Generally speaking, Seasonic PSUs are considered "cream of the crop", with ranges such as Corsair's HX series slightly cheaper but pretty much as good. [Note: both are slightly unnecessary for this system, but I always advise spending more on an excellent PSU rather than regretting it later]. Consider a HX750W perhaps? I mean, this is all overkill for that system, you are not going to pull anywhere close to 750 watts. Also consider and decent PSUs like that only reach peak efficiency at around ~ 40% load, up to say 75% load (all the profiles differ mind, and this is top of my head stats - in other words, bull____). If you're only going to pull 200-250 watts, then are you going to hit peak efficiency with a 750W PSU? Just a thought. I would have thought a high quality PSU with 500-600W would be a sweet spot - miles of headroom for expansion, but just about hitting its peak working efficiency.
If you're not prepared to spend that kind of money on a PSU, Corsair's CX range is damn cheap but pretty good too. There are many more to recommend, but these I have some experience with. I'll let others with recommend the rest
i5 2300, 16GB, Corsair HX750W, 20TB ZFS pool (2x raidz1 vdevs), 60GB SSD, Fractal Design XL
Ace2 (Primary Client)
i7 2600, 16GB, Corsair HX850W, Asus HD6970 DirectCUII, 4TB, Fractal Design R3
E7200, 4GB, OCZ GameXStream 700W, ~ 8TB, Thermaltake Xaser III