Nate,
My current room is 13x19 with a sloping ceiling (9ft at peak) that you typically see in a room over the garage. The sloped ceiling is something I've never had to deal with, acoustically, and this room has some serious bass issues.
Isolating from the floor helped dramatically, and I've also tried some cheap Auralex foam "traps". Unfortunately, for the bass region, the foam created a severe 125hz suckout without affecting any lower frequencies. Actually, I'm expecting delivery of a McIntosh C42 Pre that has the 8-band EQ, so I hope to tweak the room a bit more easily. I was real close to trying digital room correction, but I couldn't bear to digitize my vinyl.
Matt