Comment Dell + Hyper-V (Score 1) 272
I recently bought a Dell 2950 III w/32 GB memory, dual quad-core processors, and (2) 1 GB SAS drives for about $4k brand new from Dell. I am running the Datacenter edition of Windows Server 2008 x64, however, you could also run the free edition of Hyper-V. The box supports x64 clients, and is very fast and stable.
I would suggest the tower model as the fans in the rack model are very loud. I would also suggest the Dell remote management card for an additional $250. It allows you to do just about anything remotely, even loading a new host OS w/virtual ISOs.
-G