Sean's advice is good, as usual, but I'd say it's imperative to read F. Alton Everest's "Sound Studio Construction on a Budget" (which covers all kinds of rooms, listening rooms in particular). He believes in diffusion, not only absorption, and that has worked beautifully for me. If you can go the DIY route, I have instructions for DIY RPG-style diffusors and Argent Room Lens copies that I could email or snail mail to you, but you'd need a table saw for either. But if you don't yet know what an RPG-style diffusor is, read Everest first. Jon Risch's bass trap looks trickier to make, to me, than a perforated panel absorber, details in Everest. You can turn your bad room into a good one, in all likelihood. Everest also shows you how to identify resonant modes that may need to be "trapped", minimized, by bass traps or panel absorbers. That book, like his 4th edition of "The Master Handbook of Acoustics" is must audiophile reading, IMHO.