I just took a quick look at your system specs and I have a similar system, which does OK for games, but I already need to upgrade it again.
I have exactly the same graphics card I think. One reason I picked it was EVGAs support, because I originally bought another card by another manufacturer that had good reviews but it didn't work out of the box. I was able to return it but before I could return it I had to talk to the manufacturer to confirm that card was bad. What made this difficult is that there was no USA phone support.
This card seems to run Unreal Tournament 3 well and it runs GTA IV, but not quite so well. The frame rate is low, and I have read the game is buggy, but sometimes it will start to lag to the point it is unplayable. This doesn't happen every game, so I'm not 100% sure it is my system, but going by the frame rates this game could use a better card. My system meets the requirements for Call Of Duty Modern Warfare, but it's not optimal for that game, and I haven't actually tested it (I think the video card would run it OK, if I remember correctly).
I think that this video card is a good deal for the money but if you are spending up to $1000 I would spend more on the video card. In my opinion that's probably the most important part of a gaming system, but I had to upgrade to dual core and better power supply at the same time so I couldn't really afford a better one.
Upgrading my system from a single core to dual core and and adding this video card was a huge improvement as far as gaming goes. Before that the best game I could with the built in graphics was the original Fable. Not very impressive considering that would run on the original xbox, but I didn't expect to do much gaming with built in graphics; I needed a new computer and $400 was all I could spend at the time.
You might want to consider this AMD cpu here: AMD Athlon II X4 620
At under $100 it is has to be one of the best deals as far as performance to money ratio. If I have the money to upgrade my computer any time soon this is what I will be buying.