You could purchase the Rives Audio test CD and a Radioshack sound pressure meter. The test cd allows you to measure the in room frequency response and will likely confirm what your ears are telling you. From there you can explore solutions.
Where to start with room acoustics
I just moved into a new house that has a listening room (13 ft x 27ft with 8 1/2 ft ceiling). It is obvious the room needs some help. I have read some of the chapters in Master Handbook of Acoustics by Everest (although some of it is over my head). The question is how to assess the needs for this room. Where should I start?