Processor?
Answer:
I prefer the AMD processors, but since we don't know what motherboard you will be using, we cannot really recommend a CPU. I did buy my AMD 4800+ x2 at newegg for beneath 200 (big sale)!
I don't know exactly how fast you want your computer. But out of my experience, Intel is the best over AMD, but for a moment more expensive.
i hate to speak this but this is it is Intel
http://www.newegg.com/product/product.as...
but it is $222
AMD would be MY choice but it is SLOWER than the Intel
http://www.newegg.com/product/product.as...
Try sharkyextreme(dot)com's Weekly CPU Price Guide.
Intel Core 2 Duo would be your best choice.
coastmemory.com will scan your pc and hand over you prices for all upgrades.