Just my $.02...

I think the CPU is one of the cheapest parts, when you're buying the whole Shabang  I would recommend saving CPU changes for "Core" changes(of like the Mainboard;) especially if you're into Dells'/Compaqs'/or HPs VS. building your own.  I've swapped Hard Drives, RAM DIMMs, and Video Cards out of my computers, hundreds of times, but the CPU has always been another story!