I recently got into casual gaming on my pc. I bought some games and what sucked about it was that they all lagged at low settings. I just want to play most/all of the newer games. I'm willing to spend $300-$400 for anything that I might need.
- AMD Athlon II X4 630
- ATI Radeon HD 4200
- System Bus 4000MHz
- 4Gb DDR3 SDRAM
- 750GB Hard Drive w/ Windows 7 64bit
At that price range, you can afford a GTX570 (~$350), or a HD6970 (~$370). You would also be happy with a HD6950 (~$300) or a GTX460 (~$200). All will be a very significant upgrade. I would look at adding some RAM as well, since Windows 7-64 bit can use more than 4Gb (maybe GTX460 + RAM for less than $400?)
I don't mean to be a party pooper but that athlon x4 needs to go most games take advantage of 2 cores your pretty much stuck with athlon x2 performance processor wise, I would get at least a Phenom II x2 that has the 6 Mb l3 cache but then again the more cores the better but make sure it's at least a phenom II processor.
Accolyte (and Psycho Teddy) is giving good advice, as I don't know very much about the performance of different Athlon CPU's. What he is saying is that the CPU may bottleneck your video card, preventing it from reaching the maximum frame rates of it's full potential. All of the cards that have been mentioned are PCIe (PCI Express).
Definitely not enough to handle ANY graphics card that will be better than what you have. If you want to upgrade to a better Graphics Card, you should look into a 450-550 watt PSU depending on the card you choose. AMD cards tend to use less power than Nvidia. Corsair, Seasonic, and Antec are all good brands to choose from.