You're absolutely right about the importance of the room in the component chain. Many, many people do not realize this and try making changes in other areas, when simple room re-arrangement would make a much bigger difference in enjoyment.

I'm lucky that I've got a dedicated room, but the basics of it can be something to strive for:

• Try not to have the dimensions of the room multiples of each other, a perfect cube of something like 8'x8'x8' being the worst possible combination.

• Try to have your front speakers (at least) in as symetrical a layout in the room as possible. Try not to have for instance a huge open walkway into another room next to your right speaker and none next to your left speaker. Symetrical layout of the furnishings in the room will help too.

• As much as possible, do not have any two parallel walls, where at least one of them does not have some sort of acoustical diffuser (bookcase etc) or absorber (hanging rug). This will break up "slap echoes". Walking around the room while clapping your hands will identify these problem areas. Don't forget reflections from the floor to the ceiling.

• Have a friend run a mirror along the left and right walls while you are sitting in the preferred listening position and move the mirror until you see the reflection of each speaker in it. At this point, place some acoustic treatment, diffuser or absorber. This will tame early reflections from these side walls, helping the imaging.

• Carpet in front of the speakers will absorb to some extent any reflected sound from the floor.

• Keep the area around your front speaker array as "clean" from unnecessary objects as possible.

• Keep the front speakers a couple feet from the rear wall, and the side walls.

• If you have a sloped ceiling, try to arrange the system so that the slope is not for instance from right to left. Front to back or vise versa is better for imaging. If possible, hang some absorbing or diffusing material, plants or such up there to break up reflections.

I'm sure there are a lot of other things I haven't thought of, but this is a good start