I would also say to read this article....
http://www.ethanwiner.com/acoustics.htmlAcoustic panels can be built pretty cheap, compared to manufactured brands, if you have the time. Bass Traps are the most important, which go in front/rear corners and can be straddled across the corners, triangles filling the corners, or rectangular columns. Corners where walls meet the ceiling and floor/walls is also important.
First reflection panels handle mid/highs and help with echoing from hearing the same sound hitting your ears from the walls/ceiling.
Throw rugs, blankets thrown over your recliners, etc... will help, but can't absorb as much bass/mid/highs as treatments.
