Surprised noone mentioned the Phenom2, has great price/performance and very good upgrade shcemes where you didn't need a new motherboard.
It also seemed to have solved the so called performance problems of the original Phenom which a bigger/better cache or whatever.
It's also almost like a favor in the name of competition you're doing in buying these too...
I haven't used many other processors, let's see: 68000, too slow, 020, too slow, 040 good price/performance back in the day, but could have been better, 060 was very good, almost like a pentium but expensive..
I had a Phillips MSX VG8020 back in the day, but I was just a kid and mostly played cool games:) It was graphically better than the ZX
