College rocks, leave the cables exposed. It's the only time you'll get away with it.
If it's offensive, run some gaffers take down the wall to cover the cables, they sell white gaffers tape.
Cinderblocks are cheap and work well for raising speakers.
I'd say raising the speakers to ear level will make a dramatic improvement. Books, cinder-blocks, whatever, it all works.
As far as a subwoofer, check out Dayton on Parts Express.
If you plan on throwing parties, set the volume limit on your Denon to protect your speakers.... the more smashed you, friends and randoms get the louder the volume goes - easy to pop drivers.