Look what BYD is doing on a shoe string... http://www.treehugger.com/galleries/2009/01/byd-f3dm-f6dm-e6-china-electric-cars-plug-in-hybrids- photos.php And it's is aimed at the working man rather than the sportscar crowd!!

I won't get into the debate on "name brand" verses "whitebox" or do it yourself.
I am a teacher so money is an issue for me.

Things I have found that work for me in a lab (rather than production environment):

dual or quad processor (AMD seems to work and lower $)

processor / mother board support for hardware virtualization

Lots of ram ( I use x64 OS with 8-16G)

Choice of vm technology - Virtual PC/Server is find for MS based guest but
                                                      VMWare Server all the way for anything else

I don't get too wrapped up in RAID solutions, HD are cheap and DVD backup is even cheaper

If you need to backup/change out vm machines consider building an Openfiler NAS. It even
supports iSCSI if you have the funds.

First and foremost, vm's can be a fun learning tool.

GP