Depending on your ceiling height you could actually have a wonderful room. Certainly 18 x 24 dimensions can accommodate all but a couple of the largest speakers out there. The concrete walls are a great asset and will help the bass and add solidity to the sound. Yes, your room is probably bright and reflective right now, but it could have a lot of potential. Its much easier to tame a hard room than try to bring life to a dead one. You'll certainly need room treatment and need to work with knowledgeable people on this. Pile thickness of a rug is very important for its acoustic benefits and character. The wall treatments should be chosen very carefully as well, many of commercial audiophile products do little to help with reflections and if anything do more harm with their coloration. If your ceiling height is 10' or more, you could have an amazing listening room.
