Drapes are best on a large picture window. Carpet is good, start by not having the audio rack in the middle of the speakers, have it between the first and second reflection points. Find these points after you try the 1/3rd or 1/5th room set up method. (Have speakers and listening chair 1/3 or 1/5th of the way in the room) You can even combine the measurements,speakers 1/3rd and chair 1/5 of the way in the room. Sit in your listening position and have a friend run a mirror along the wall at speaker height, have them stop and mark the wall when you see the same side speaker. The second reflection point is when you see the opposite speaker ie. mirror is on the left wall and you now see the right speaker.
Hang a small (2'x4') rug on the wall covering the mid point of these areas. You can get a cheap thick bath rug at Target or Kmart for a couple of bucks, also garage sales are good as well for oriental style ones. GIK sells a fantastic room absorber for $50 or so per, the 2" thick one is perfect for reflection points, but don't buy anything until you determine this is your problem. This will tell you if your room is bright or dull. These are by no means the end all, be all of room treatment but it is a good affordable way to start, if you hear no difference then investigate equipment changes, I usually change one item at a time, trying to avoid the old too many variables syndrome.
