deffinaltly, an look at AMD processors, they are cheaper, but you can still get a quick quad core processor... also, try selling the graphics card you have and use that money to buy at least a Radeon 5770, i reccoemend you try to find the funds to get into the 58xx series graphics cards, the cheapest of which is the 5830, then the 5850, and finally Radeons single GPU flagship card the 5870 ( which i have and im in love with it ).
are you planning on over clocking the CPU? thats another way you can supercharger your computers performance for almost free ( the cost of keeping it cool, anywhere from $30 - $400+ depending on how crazy you want to go ).
remember, bling cost money and doesnt help the processing power of a computer at all... go with a antec 900 or 300 and save an extra $80, go with a 640gig hard drive instead of 1tb and save $40, i dont know much about mother boards,but i think yo have an over kill mother board, get a $180 mother board and save $140, add all that and you have an extra $260 that you can put into your graphics card, ram and processor and it will run much faster.
with budget gaming machines you have to focus as much money and energy onto components that impact performance, IE CPU, GPU and RAM.
so look into AMD processors and Radeon Graphics cards, if you this procsessor with this graphics card you will be good to go!
Newegg.com - AMD Phenom II X4 965 Black Edition Deneb 3.4GHz 4 x 512KB L2 Cache 6MB L3 Cache Socket AM3 125W Quad-Core Processor
Newegg.com - SAPPHIRE 100297L Radeon HD 5830 1GB 256-bit GDDR5 PCI Express 2.1 x16 HDCP Ready CrossFireX Support Video Card w/ ATI Eyefinity Technology
EDIT: also, try to find combo deals, like the mother board and processor you want in a bundle and it will save you another $25. also, look for these parts in other places than newegg, craigslist, amazon, tiger direct, shop around and find the lowest possible price for each component and save your self as much money as you can, so you can focus those funds into parts that increase the processing power of your computer!