I've come up with the following list of components that should make a decent server using Hyper-V to experiment with various versions of SQL Server, Windows Server and also run Windows Home Server:

CPU Intel i7-860
Motherboard GA-P55A-UD5
CPU Fan Noctua NH-U9B-SE2
RAM 2 x 4G Kit DDR3 2000 Kingston HyperX
PSU Antec TP 550
Video 512MB 4350 Gigabyte
Drive (System) A-RAM SSD PRO series 32GB 2.5" MLC SSD
Drive (Data) 2 x WD 1.5TB
UPS Socomec NeTYS PE 600Va UPS

Most parts I'm planning to get from MSY with the exception of the SDD and UPS which I'll get from MATS Systems. I've seen comments that while MSY sell a cheaper SSD, the Indilinx-based drives (such the A-RAM) perform much better. The video card is the cheapest I can find, as it will be hardly ever used (there isn't any on-board video on the motherboard). The i7-860 has 4 cores and 8 threads. It uses the 1156pin packaging and seems to be reasonable value if you don't want to step up to the 1366pin 950/970 chips (which then require more expensive motherboards and RAM). I'm thinking that a UPS might be a helpful addition to ensure this machine gets treated well as far as the power supply goes. The motherboard has plenty of USB and SATA connections so should offer room for future storage expansion. I may end up throwing in some of my existing older/slower drives into this machine so that the Home Server can make use of them too. I'd appreciate any suggestions/comments too.

Update: 7-Feb 9pm