For less than $2000 you can get a nice ESX 5.0 physical server (or two possibly) with a Fibre Channel SAN/HBAs and a gigabit network switch from eBay. From a long-term perspective, that would be a much wiser choice than dinking around with trying to make a desktop box work and would be a much better way to spend your $2000. It'd give you a place to expand in the future.
You have to be patient and know what it is you're wanting on eBay and don't buy anything from anyone who doesn't have at least a 98% rating. Heck, I just saw a Dell PE2970 on eBay a few days ago that sold for around $200 -- you could put 16GB of memory in that server and 2x quad-core Opteron CPUs in it and do the entire server for under $500 on eBay including a 2G PCI-e HBA. My PE2970 runs ESX 5.0 off a USB stick and the VMs are located on shared storage. That PE2970 also runs nested hypervisors which in turn, have their own nested 64 bit VMs.
Note that the amount of memory will usually be more important to your home lab than pretty much anything else. That's why if you buy a real server (HP, IBM, Dell -- whichever is your preferred brand) it'll be a better initial investment since you can usually pile more memory into a real server. I'm buying ECC memory for $22 per PC2-5300 2GB stick on eBay right now and less than $50 per 4GB PC2-5300 ECC stick.
Also, if you're storage is slow everthing is going to be slow -- that's why an inexpensive Fibre Channel 2G SAN for shared storage, even with 10K 73GB disks, would work well for now and in the future since you have $2000 available to spend on the home lab.
From a CPU standpoint, make sure you buy CPUs that support fancier virtualization features, not just regular hardware VT-x and AMD-V virtualization (in AMD those fancier features would be RVI -- only available in 3rd Generation AMD Opteron server CPUs -- 13xx, 23xx and 83xx series of AMD Opteron CPUs). Having the fancier virtualization features in the CPU gives you way more options now as well as in the future (system BIOS also needs to support hardware virtualization also). I'm buying 3rd Gen AMD Opteron quad-core CPUs for $50 each on eBay (you'd need a matched pair for a 2x CPU server).
Also, make sure everything you buy, from a networking perspective, is gigabit speed (NICs, network cables, switches) and if you can get a deal, get the network switches with Jumbo Frame and VLAN capability.
Datto
