The $500 Upgrade
The $500 upgrade is based on the two components we've used before, the Athlon 64 X2 4200+ Socket 939 dual core, and the Seagate Barracuda 7200.10 500 GB SATA hard drive. We did not go for an upper mainstream graphics card, but for a high-end model. The GeForce 8800 GTS by Zotac is an exemplary choice; other brands provide similar performance, and fans of the AMD/ATI Radeon HD 2000 series will find an appropriate alternative in this camp.
This option represents the maximum upgrade that we would still recommend for a two-year old system. Yes, you could try to get a faster Athlon 64 X2 4800+ for Socket 939, and a high-end graphics card such as the GeForce 8800 Ultra or a Radeon HD 2900XT. However, the processor would cost you unreasonable amounts of money (as would the graphics card), and it would still bottleneck both graphics cards. In addition, you should pay attention to the graphics card's power requirements, as one of the latest top-of-the-line cards could demand too much power from your power supply. A 400 W PSU will work with the GeForce 8800 GTS, but you might run into trouble with more powerful models.
This $500 upgrade option certainly is controversial. We believe that if you spend that much money on upgrading an old system, you should certainly also invest into upgrading the RAM to 2 GB. I personally don't like the idea of spending so much money on upgrades, as an entirely new system (motherboard, RAM, processor, graphics card, hard drive) is not much more expensive.
