Ya my suggestion is if you insist on one computer but multiple mid level computers for the same total price will always be better then one super computer at the same price, I have 6 computers.

Although if its for 5 boxing or less 48G ram on one computer might still do better then multiple computers (but he can 3 or 4 for that much with older parts), as he will have the whole wow folder in ram. You just might not want to be stuck with a server computer.