>>>Update<<< NEW LION INSTALL GUIDE:
Apple made the transition to Intel processors in 2005, two weeks later a hacker called Maxxus installed OS X on a pc running Intel cpu. At the moment we have AMD and INTEL releases of OSX86. Since Apple is using Intel Core-Duo processors is possible to install nearly original OSX (Vanilla), only by applying EFI (type of OSX bios) to the install. When you are about to install OSX on your machine and you are thinking to upgrade the cpu, I would recommend to upgrade it to the newest Intel chips. The advantages of this move are compatibility and performance boost comparing to AMD chips. I newer installed OSX on an AMD machine, but I know from many sources about it poor performance towards Intel. If you have an older Intel chip, you have to check if it supports SSE3 instructions, which is very important if run apps like FCP. You can do that with a small program (500k) called CPU-Z, run it in windows and you will get the info about your cpu, mobo and petty everything what you have in your box.