Any recommendations on how to get to a PC that is SFF-ish in size, quiet, and can hold 4 to 5 3.5" drives, or on my possible solution above?
The ASUS T3 Terminator Barebones are pretty quiet.
Plenty of room for 5 3.5" drives, though I would recommend getting creative regarding mounting. Also only has 4 SATA ports with one being external, but there's always PCI and PCIe slot for another controller. The included 250W power supply isn't horrible--standard ATX w/ 120mm fan. Makes a nice LAN party box except for the lack of overclocking. ASUS has a 3 year warranty on their bare bone systems.