Take a look at http://www.ibuypower.com/Store/Intel_B8 ... nfigurator. For 1000$ you can make a computer with an i5-3770k CPU, 8GB Ram of your choice, a Radeon HD 7850 2GB Graphics Card and a z87 Motherboard to top it off. Again, this is not the best computer out there but It is a fairly good computer for the price. And it is a hell of a lot better than the walmart crap. Hope this helps
Okay, I'll take a guess and say you are looking for a prebuilt gaming PC, i'll configure one up for you at a few of the major gaming PC builders. I recommend ditching that computer and just buying a new one however, no point in upgrading that one.
Everything can be done, It just depends on your price range. Tell me your price range and I'll look at some options for you. A mid-high end gaming PC could cost you between $1,000-$2,000 so if you want something that will last quite a long time and something that is able to play numerous games on MAX settings, this is roughly how much it would cost.