Everything above is correct. It could be a lot of things. The reflective room hit me before I even read all the posts. Have you tried different angles with your speakers? A lot of guys with high end equipment tend to bring out their front mains into the room, a few feet from the wall, and canter them just behind the listening area. Acoustical tiles are popular on the walls. In your case, possibly the rear wall? It's hard to say without seeing your layout. Any chance of posting some digital pictures? Finally, what do you think of your tweeter? (1" Tioxid 5 inverted dome tweeter with 3/4" coil). In an article taken from Home Theater Magazine on similar speakers, they wrote "dubbed TNC, this new tweeter features a special low-density aluminum/magnesium alloy formed using a similar technique to the Utopia's beryllium dome, which is claimed to endow it with incredible rigidity and lightness while retaining excellent damping properties. In plain English, this means that the TNC tweeter is touted to combine the best aspects of a good metal dome with those of a soft dome in one budget-priced offering." If this is the same tweeter, it may not act exactly like a very high end soft dome would, especially with strings.