About two days ago, I rotated my whole living room 90 degrees (well, the contents thereof). It made a dramatic improvement in sound, just due to room orientation (doorways, walls, etc.). The room is pretty bright, with laminate floors and drywall. My Ascents now have bookcases behind them which breaks up a problem I had with a reflection causing excessive brightness in part of the range.
Unfortunately, I probably need to buy some miscellaneous new furniture because of the new arrangement. In particular, the speakers now flank a masonry fireplace, making positioning of video for HT a bit of a problem. The audio and video electronics were in an oak wall unit, which is on what is now a side wall. In the interim, I moved my CRT Sony directly in front of the firebox on the hearth, but am now looking at a 46-52 inch RP-DLP as a replacement. The DLP will be light enough to move if I get in the mood to build a fire. I thought about a front projector, but the room just doesn't work very well for that. My goal is to build a new home sometime in a year or two, so I'll plan out a listening room from scratch then.
The September issue of Fine Homebuilding has a product announcement for a special sound-reducing drywall product composed of multiple layers, including drywall, rubber membranes, and steel sheeting. It's not cheap though, at about $80 a sheet. It's supposed to be the sound reducing equivalent of eight layers of 5/8 inch drywall.