Comments I've read from owners of the new Mac Pro seem to indicate that the best platform for running Vista (among other things) is... the Mac Pro!.  I priced Dell and HP 8 core PCs, and the new Mac Pro beats them in price (and I think, quality).

I intend to buy the 2.8 Ghz 8 core Mac Pro soon, and use Boot Camp to run Vista.  BTW, make sure to use at least Vista Business 64 bit, if running Vista on the Mac Pro, 'cause Vista Home Premium will only see one processor.

No wonder Apple increased sales 60% last year, and now has 16% of the PC market (it was as low as 3-5 % not long ago.  This is great to finally have Apple producing some of the best bang-for-the-buck computers in the PC marketplace.