What type of processor should I get?
AMD or Intel?
While AMD has the flat out fastest single core and double core processors, certain brands run Intel chips only. Dell only recently started making commitments to sell PCs with AMD chips due to customer demands. AMD chips with Dual Cores offer 2 processors on one chip with crossbar circuits (hyper-transport technology), so the 2 cores can communicate with the memory rather then Intel, which relies on the mother board to allow the 2 cores to communicate. AMD Athlon 64 X2s are the future with the latest model being the 4800 at around $850. (chip only) but can be used on most AMD compatible motherboard with the 939 socket and a minor Bios update.
Intel's Extreme Edition 955 Dual core is a 3600 that includes hyper threading. If your using software that can take advantage of hyper threading such as Photoshop, you will experience less waiting.
The reason I'm pushing the dual-core processors is that you can be burning a disk, while typing a document and simultaneously Download your email as you have 2 processors to share the load.