Sonnet has upgraded their xMac mini Server housing, adding support for a full-height/full-length x16 PCIe card, three USB 3.0 ports, and a Thunderbolt pass-through port.

If you’re not familiar with this product, it basically turns a Mac mini server into a 1U rack mountable blade server. It includes it’s own built-in power supply (replaceable) and quad fan system, and support up to two PCIe cards.
http://www.sonnettech.com/product/xmacminiserver.html