I have an almost identical setup hardware-wise (I opt'd for dual 2687 v2s [better single core performance]) and it only cost me $1000. It also supports 20 physicals disks with no extra hardware or configuration needed (aside from just plugging in the disks and adding 'em to ZFS).

RAM (DDR3) and storage capacity (cheap SAS drives) in these systems is really where the savings is... I don't think I'll ever own a "regular" desktop again.