The board that jumps out at us is the ASRock 939Dual-SATA2 motherboard. Not only does this board provide the CPU generation support we think is best, but it also allows us the choice of either PCI Express or AGP video cards as well as SATA2. Giving us choice for all the economical components with support for future expansion at an impressive price point ($69) makes this an easy choice.
Athlon 64 Processor
Image source: NewEgg.
Now that the motherboard platform has been decided upon, we need to select the processor. With our cap at $500, we chose the AMD Athlon 64 3000+ based on the Venice core which puts us at just under 2 GHz (1.8). There is an excellent chance that 2 GHz or more can be achieved easily with only moderate overclocking, should you be into this. Currently this CPU represents one of the best bangs for the buck. Venice is a mainstream core with 512 kB L2 cache. At $140, it is a good entry point for our CPU. There is no need to go for a CPU cooler when purchasing a boxed CPU kit.