On benchmark sites I've been to, the Intel P4 processors have the top/high end, and the competing Athlons are not quite as fast (not taking into consideration overclocking, mind), so perhaps if you had lots of money, Intel is probably your best bet.
I'd probably get an Athlon (2000+ series like Doom said) myself, though, as they are much cheaper as the only thing that will tax it is N64 emulation as PC games tend to be graphics card intensive these days.
You could wait for the 64-Bit Opterons etc. if you hold out for a few more months and want the best.