Best treatments are room shape, size, insulation, and dedication. Tiny squarish rooms are the worst, suggest reading Floyd Toole's "Sound Reproduction". Uninsulated means your noise floor is high, so you have to turn it up more to overcome (hard on your ears and on those sharing your place). By dedication I mean dedicated and optimized to audio. Anything short of following these principles is fighting against the laws of physics.
Second best treatments is multiple subwoofers to control inherent in-room bass peaks/dips. I have three subwoofers (again read Toole) and ten GIK (find them here at AC, the most effective available) absorption panels in my 8ft x 13ft x 21ft insulated/dedicated room with mid-field setup away from all walls. The GIK panels consist of six 2ft x 4ft 244 wide range panels (located at all first reflection points) and four 2ft x 4ft bass traps (straddling the front corners). Panels do little is this "perfect" room (but instantly perform miracles elsewhere). Have also tried a couple of DSP options on top of the subwoofers and panels but my small audio club was undecided on whether it was an improvement or not.
