Personally, I'd go with a small form factor, like something from Shuttle -
http://us.shuttle.com/ - just for the desk space and potential quiet if you get fairly good one.
Next up would be something more complicated in a tower with liquid cooling so I wouldn't have fan noise.
SATA is a must now. And you might consider some form of RAID too.
I'm sure you'll have some issues but you'll have fun too!