For the type of Gaming you want to do your system looks plenty good.
You could in fact though - get a better Vid card for the same cash - roughly.
BFG has the GT version for $139 at newegg... there are also some others ranging around the $150 mark(all 7600GTs)
$50 more bucks and you could get http://www.newegg.com/Product/Product.asp?Item=N82E16814150216"
rel="nofollow">The XFX PVT71GUQF3 GeForce 7900GT 256MB