You guys should check out www.atlargenutrition.com Not sure how it stacks up with prosource, but i've been happy with the stuff to price ratio.
What i like about prosource is not only the prices but the huge selection. Im not trying to sound like a salesman here, im just partial to them lol. I have heard good things about bodybuilding.com too tho.
@Frank, yep thats pretty much what I said.