Im using a Power Mac right now. It is a little older, but Im looking at the G-5 when I get some $$$. As for the specs, Im not sure yet. I know I have had trouble with the mac I have now, being slow...so I imagine a lot of RAM is a good thing. I have 3 80gig hard drives...one internal and two external for photo storage. And have plenty of room , just it can be slow.
I was talking to a Msc rep the other day, and he suggested the Mac Mini. If I get to see him again soon, I will forward any info I get.