Hi,
we were looking for inexpensive and energy efficient micro servers working with VMware vSphere 5 for our Lab and testing. These models worked just fine (although they dont have any VMware Certification, so you wont get support from VMware) :
Fujitsu MX130 S2

• Dual-Core AMD Athlon II X2 220 2,8GHz
• 16 GB RAM max. (4 x 4GB DDR3 1333 ECC unregistered)
• onboard Broadcom GBit-LAN (tg3)
• 2 non-hotswap 3,5″  SATA drive bays
• 2 x HDD 500 GB
• 4 low profile expansion slots (PCIe x1, x4, x16, legacy PCI)
• power consumption 48W (vShpere 5.0 running, no active VM, without harddisks)

 
HP Proliant N40L

• Dual-Core AMD Processor 1,5 GHz
• 8 GB RAM max.
• onboard Intel GBit-LAN
• 4 non-hotswap 3,5″ SATA drive bays with SFF-8087 connector
• 1 x HDD 250 GB
• power consumption 42W (vShpere 5.0 running, no active VM)
• nice: Set of screws and screwdriver on the back side of the front door, USB connector onboard, boots vSphere from USB

IT is exciting,
Christian Eich