MONITOR RESOLUTION:1920x1080 (this is the reason I mentioned of low graphics, lowering resolution etc..)
ADDITIONAL COMMENTS: Preferable to run under default or 400W power supply)
Actualli I have no idea about the recent nVidia cards like the 200,400 series etc.I checked the Sparkle GTS 450 (within range) but will be good or is there any better option for that.
The 7750 should perform about as well as the 6700's but with dx 11.1. I suggest you get 7750 as its more up to date and you will have no problems finding 7750's later for crossfire. AMD stopped production of the 6000's so it could be hard to find a second later. Also your 400w should have an easier time pushing this card as it requires a bit lower power. http://www.newegg.com/Product/Product.aspx?Item=N82E168...
notice that the7750 beats the 5770 in directx 11.