does it absolutely HAVE to be 1u? if you can go 2u we've been really happy w/HP DL385s lately. 2u form (which is still pretty small for a DB server), redundant power supplies (a good thing for DB server), six drive bays (so you can RAID5 or three mirror pairs), remote management card and Opteron gives you a 64 bit path w/o sucking in 32 mode.
I have eleven of them (so far) and don't think anything can touch them on a bang/$ basis...
