If you want the best of the best i would buy a Boxx system (lol), you probably have to take a mortgage on it though

But serious;

-processor; intel core2extreme(QX6850) or core2duo(E6850).
I wouldn't recommend buying a quad core because maya most of the time runs perfectly on 1 core only wen it comes to rendering the other core kicks in.
-RAM; at least 2 GB of RAM, prefferably 4 gb
-videocard; In my previous computer i had a NVidia card, but when i was compiling a list for the components for the new computer i heard some good things about an ATI card(ati radeon x1950xtx), but in maya this card sucked on the field of viewport performance, the drivers from ATI also suck, BUY NVIDIA!!!!!!!.

Good luck