The X-Serve is actually a viable server - it has a Radeon X1300 with 64Mb RAM, and 2 PCIe slots. Enough for another graphics card and a Decklink Extreme. It also supports SCSI or SATA - the Mac Pro to my knowledge only supports SATA drives internally - unless you bodge the SCSI drive into the spare optical drive bay.

Interesting...

Hugh