I saw this one tonight. It is an older X8 platform but it is also the Supermicro SBB platform which was for adding two SAS controller nodes in a chassis.
Manual: http://www.supermicro.com/manuals/superserver/3U/MNL-1186.pdf
Currently selling for under $400 shipped but it is an auction: SUPER MICRO SERVER 4X5650 CPU 2.66GHZ 24GB DDR3
If you were looking for a SAS HA head setup, this might be a very inexpensive option. I think these do require SAS drives not SATA.
Manual: http://www.supermicro.com/manuals/superserver/3U/MNL-1186.pdf
Currently selling for under $400 shipped but it is an auction: SUPER MICRO SERVER 4X5650 CPU 2.66GHZ 24GB DDR3
If you were looking for a SAS HA head setup, this might be a very inexpensive option. I think these do require SAS drives not SATA.