We've got a decent-sized living room (~15x20x9 feet), and there's a fair variety to the geometry (coffered ceiling, bay window, open wall to dining room, etc.), but the floor is all hardwood or ceramic tile, and there's an upright piano between the living room and dining room so it's really "live" in there. One large and two small windows with fairly heavy weight fabric curtains. The seating is against the rear wall, and the front wall is mostly taken up by the screen, and the WAF, which I assume stands for Wife Approval Factor, is quite high. Upholstered walls, she could deal with, but not if it means 2+ inches of (add your favorite absorption material here).
Any suggestions on how we can tame the high frequency reflections without adding thick material to the walls?

Thanks,
Jeff

Treat the ceiling:
http://www.owenscorning.com/quietzone/products/products3.asp?id=smenu8