All of us have excuses for why we cannot acoustically treat our rooms but a lot of the underlying reason is that many are not convinced that they should make the physical or financial effort. I’ve discovered what I think of as training wheels for room acoustics. Tom Gorzelski of mytheater acoustic panel showed me his simple and inexpensive kits; these are enough to get anyone started. The panels are only 1" thick and, with their polyester filling, light enough to hang with a single nail. Don't expect them to work into the bass, therefore, but Tom acknowledges that they are most effective at 1–2kHz. Also, they come in packages of four 24x40 panels ($120) or two 24x24 panels ($45) because you cannot expect just one to make a difference. Still, hanging a 4pack of the bigger panels should reduce reflections if placed at ear level and, especially, at the first reflection points on the side-walls. It's likely you'll like it enough, perhaps, to do even more.