Decent hardware (< $1.500) for Hyper-V dev/test machine
Solution 1:
About the silent part - I did a writeup recently on how to build a silent PC using the Antec Mini P180 case. I've been very happy with it - even with five SATA drives, it's hard to tell it's running. I'm an Apple fanboi, all about the silent machines, and if I say it's quiet, it's really quiet.
http://www.brentozar.com/archive/2009/05/how-to-build-a-silent-pc/
Solution 2:
I just bought a new machine from ecollegepc and had it shipped to Denver for $740 to my door in less than a week. Unless you really want to build it yourself, not sure that you save much from NewEgg.
I got: Intell Q6600 8MB Cache (quad core) 8GB RAM (2 4x) 2 x 500GB 1GB nVidia card.
I put Hyper-V on it and it's running great. Adding 3 more drives would be about $600, and I'd be below your $1400 without going through the hassle.
Not sure about more memory, but at the point where you are spending $1500, I think a system builder that will warranty things is not a bad plan.
Solution 3:
I have an HP ML115 sitting in my basement right now. Quad Core, 8GB Ram, dual 1TB Raid 1 Drives. Runs like a champ and is quiet.
Best part is it shows up already built, no muss no fuss. I have it running 3 VM's.