Antec Titan 650 case, antec 430W power supply (which is probably overkill), Intel RES2SV240 sas expander(which seems to have gone way up in price, i think i paid about 200) . supermicro cse-m35t for a 5 3.5" drive in 3 5.25" bay adapter. 10 WD Green 2 TB's in Raid6, off the 3ware 9750-4i. 2TB WD black boot drive. Case is full.
Motherboard is an ASUS P8H77-V, Pentium G630 cpu, 8 gig ram. I have an I3-2100 in a media server out front so if I need more power I can just swap them. The server draws around 100W at idle.
Has no difficulty keeping up with anything I need, network copies run at about 115 mbyte/sec to/from the Windows machines. Reads locally are in the 400 mark.
Things I'd do different:
I'd go with a quiet rack case with more bays. Maybe even one of the cheap 3U/4U Norco units. Supermicro is much nicer though.
WD Red instead of WD Green. Red's didn't exist when I put this together. Green is a really bad idea because of WD crippling the firmware on them.
Probably start with 4TB drives instead of 2's, I've upgraded this thing twice already.