I would go with a Xeon-D setup or a C3xxx Avoton based setup. Depending on your requirements you could even get away with a NUC or other small form factor lab. I am running two setups. 3x node Xeon-D cluster for my production lab and 4x node 8i5BEH NUCs for dev/test. My power consumption is around 600W with all systems online, switches, router, and UPS. Most of the time the NUCs power dow and my minimum wattage is around 240.