Talking about this with some friends, they realize the SLI option is not possible.
My motherboard is Crossfire capable only.
They told me there are some tricks, but nothing official.
Reading your answers, things are clear
from 660Ti to 680 in Nvidia
from 7870 to 7950 in AMD
Like RCoon said in the first answer, Green vs Red.
Now I know the options.
Thanks.
Obviously, money is a concern for you if you're sticking with a 965. You can find the reviews yourself but I will promise you that the 965 OC to 3.8ghz will still bottleneck you in some games(games that are more CPU intensive). The first game that comes to mind is Star Craft 2. It doesn't matter how much OC I did or what graphics I use, it stuttered like crazy and frames dropped to the single digits when a big battle happened. Now I use an i5 3570k with 7850 with no OC on anything and it runs like butter.
for your CPU a good match would be a radeon 7850 or a regular 660 at the most. Anything higher is a waste of money as your marginal gain is not worth the extra cost. Use that difference to get a better CPU. The 7850 will play all the games out there anyways. Unless you really need to play metro 2033 at ultra settings, you don't need to go any higher.
Check out this thread as this guy is obviously CPU limited by the games he plays. He is using a 7950 and phenom II 965.
http://www.techpowerup.com/forums/showthread.php?t=180286
I would pick N670 for gaming. NV's driver is much optimized. recently, there are some models with more memory sizes like
GV-N670OC-4GD . if you're AMD lover, you can pick 7850 which can be automatically overclocked by AMD boost to additiona 100MHz around. the backdraw is high fan speed (higher nosie)
ignore this "nvidia's drivers are better" BS. Both brands have equally good good drivers. Both drivers have problems. Both companies tries to fix bugs, glitches, and performance issues as quickly as possible.
There are products with more memory sizes on both brands. The 7850 can OC a lot more than 100mhz.
Both companies makes good cards and are on par with the price/performance. If you plan on OC for free performance then a 7850 or 7950 are the champs IMO and the general consensus. If you want CUDA and PhysX then Nvidia is the only option. SLI is still slightly better than Crossfire IMO. Right now, the current game bundles makes AMD the best value if those games matters to you.