21' 13' room: long wall vs. short wall placement


I know there is only one real way to find out but do you think I would have success setting my system up the long wall and sacrificing the distance behind speakers - that is so important with Avalon?
Given the furniture and cabling to rearrange, I would first like a consensus from those who tried and succeeded that way.
beheme
I have a 13 foot by 21 foot room and have the speakers on the short wall about 5 and a half feet from the rear wall and around 21 inches from the side walls. It's interesting that every speaker I have tryed sounds the best in this position.
I have found that with big speakers (I have tried Cello's and my present B&W800's) and the long wall wins big time.

My room is 15X25.

Richard
Bob suggests a great loacation....the positioning well into the room is extremely important and something many audiophiles do not recognize (it will reduce comb filtering in bas frequencies)
I have a 27 by 15 room (actually a few feet narrower in a few closet nitches). The long wall setup avoids the strong sidewall echo. You may have to treat the wall behind your listening area, I used echobuster panels. Check for slap echo by clapping your hands in the room.

Tom