XP 64? use or not

Building some computers for my friend and it just hit us we might need 64.

specs are intel core2 quad, p5e asus, 8600gt, with 4(1x4) gigs of ram.

these are for rendering with maya mainly and ive never had a need for 64 with my own computers. should i download, i mean buy, 64 or stick with oldschool xp

>>8
I don't get it.
The processor is twice as large, twice as complicated, four times as hot, eight times more power-hungry, and computes slightly faster because it can add two numbers at the same time (disregarding that you'll have to do some hundred instructions more compared to IA-32 to get the two numbers into a 64-bit register).

Oh, and it includes a 32-bit compatibility layer which complicates the processor to the level where it is completely useless.

Get an Alpha.