What is the best set-up for a college dorm room? They're not built for acoustics and the set-up is going to be temporary anyway. New but cheap, or old and whatever?
To be honest, something you're not afraid of getting stolen or damaged. If you have a decent computer with a decent soundcard, I'd go that way. Get a set of good speakers with a sub and call it a day.
Granted, it's probably not THE most practical setup, but....
A buddy built a pair of Wayne's 2Pi speakers from a kit, and had them sitting on stands in his dorm room. They were driven by a simple, single ended triode EL84 amplifier.
That system sounded quite nice indeed, especially for something that cost so little! The levels of imaging and soundstaging that it attained were nothing short of remarkable considering the small room and its crummy acoustics. I would've loved to have heard it in a proper room.