A 280 GTX would match that system the best. Also if you are overclocking up into the region of 4ghz you will need to buy some 1600mhz ram to give you room to breathe. Also go witht he asus motherboard.

first of all, you get what you pay for

I (and just about anyone else in this forum that understands hardware) will recommend you the P6T Deluxe... please don't get the gigabyte... not if you want to OC that i7

I know it's more money, but I also recommend the 285... if that's too much then just get the 260 and clock it yourself. that's actually what I'm running

Wingo is right. if you want to clock that i7, don't even bother with the 1333, that won't get you anywhere to be honest. get at least 1600-2000 and you're good to go to 4ghz easy if you have good temps. get this cooler:

http://www.quietpcusa.com/Thermalright-Ultra-120-Extreme-1366-RT-Quiet-CPU-Coole...

with some good OCZ Freeze thermal paste applied correctly and you are good to go

the 260 has performed better and cooler than I ever expected. I overclocked the crap out of it. from 576mhz (quite slow compared to the newer ones out there now) to 670mhz. the shader from 999 to 1200. fan still running at the stock and quite silent 40% with temps well under control. tested several times and no problems during testing or gaming for hours.

I imagine if you're able to get your hands on one of the OCed ones you might be able to OC it even higher than what you might reach on the non-OC cards.

just make sure you have good air-flow on your case to keep it at the right temps

I understand the price dilemma. but like I said, you get what you pay for. if you were to get some cheap hardware, you'd get cheap performance. good hardware, equal performance.

good luck, let us know how it goes or if you have any questions