If you want to see an example of how far you may have to go in a small room to get a flat response, here's mine:
http://www.gearslutz.com/board/attac...s-leftview.jpg http://www.gearslutz.com/board/attac...-rightview.jpg
That's 10" deep behind the monitors. 16" above my head. 10" in the floor corners. A full unopened box is on the floor behind the speakers. 6" traps in the ceiling corners, with some spare stuff thrown in behind them. 4" ones on the walls for the first reflections. And 8" in the corners behind the speakers.
With a LOT of experimentation trying different variations and placements (of the deskt and monitors as much as the traps), I've gotten this room to within a couple dB of flat except for one cancellation around 65Hz, which is fairly narrow. That one still bugs me but it's livable.
It looks bad, but I'm the only one who ever sees it, so functionality is far more important than looks. And it's very nice to be able to mix and know that the bass I'm hearing is really what's there and to be able to do volume automation and know I'm not just automating my room.