For the hosts in my home lab, I found some Dell R710s on ebay that came with rails, two power supplies, and an Enterprise iDRAC card. I upgraded the processors to dual X5670s (6 core, so 24 logical processors per host), and the RAM to 64GBs. Just that configuration brought each host up to ~$850 shipped (though mine have an additional Intel I350 quad port 1Gb card and an Intel x520-DA2 10G card, which would be an additional ~$180).