Buying a new Mac for FCS 2 - Need advice

Hello Good People of Creative Cow,

I am in the midst of preparing to purchase a new Mac so i can better accommodate Final Cut Studio 2- my old G5 just doesn't cut it with Motion and can't even run Color.

So I am wondering what people would recommend for powerful and efficient running of Final Cut Studio without breaking the bank. Obviously the most suped up MacPro would be most ideal, but I've heard that the new iMacs, particularly the top of the line ones do an excellent job of handling Final Cut Studio 2, both HD footage and working in Motion in Color.

How well do Motion and Color run on a top of the line iMac? Is there something so amazing in the MacPro that it's worth making the extra sacrifice to buy one instead?

I look forward to some useful feedback and thank you in advance...