My old home servers a.k.a. discarded desktop pc's had to make room for something new. The point was, I just didn't feel save anymore concerning fire danger because of old flammable mainboard components. Beside that, those old devices had been really power-hungry.
So, I got myself a demo pool device again… a Lenovo ThinkServer TD230 with an Intel Xeon E5503 dual core CPU. Though I upgraded the CPU to an E5504 quad core model… four cores are just more fun. To get the most out of it I filled the memory slots to the max one 64-bit-CPU is able to handle which is 16 GB. The TD230 is 100% vmware vSphere Hypervisor (ESXi 5) compatible so.. that's what it's running now. So far, the hypervisor is hosting 3 virtual machines based on Ubuntu Server 64 bit (since Debian was a pain in the a$$ on ESXi).

One thing remains unsolved so far. To make ESXi interact with an UPS some mumbo jumbo has to be done which is a little too time-consuming for me at the moment.