I thought it only fair that I post back here. I picked up my new PC a week ago, and although I'm only just starting to get it set up and configured, so far all is going well. (And PT works! Yay.)
Here's what I ended up with:
Gigabyte GA-H55-USB3
Intel Core i7 870
WD Caviar Black 500GB
Antec TP-750 Truepower New PSU
ASUS EAH5450 Radeon Silent 1 GB
G.Skill Ripjaws X Series DDR3 1333MHz (8GB)
Antec P193 V3 Enclosure
I selected components based on what works with PT and noise levels. Overall, it's very quiet, just a gentle "whoosh". The ASUS video card is fanless, and the other components are well regarded for quiet operation. The noisiest thing is the stock cooler on the CPU, which I will probably replace at some point.
I booted my MDD G4 "Blowhole" to check plugin listings, and can't believe how LOUD that is!
Ray