I have always had problems with brightness in my system also. My listening room sounds similar to yours, basement 22' x 14' x 7' cement with two stacked wool rugs. I have Sony XA777es, EAD sig. processor, Ayre amps, cardas reference cables and Northcreek Rhythm Signature speakers with Kevlar drivers.
A friend but the same speakers with carbon fiber drivers and his sound much smoother. I just broke down and bought a set of the carbon drivers and you know my system isn't bright any more! I know this doesn't help you but I spent years and a lot of money to "smooth" out my system (bought equipment that is know to sound smooth) with our much luck and low and behold it was the speaker cone material all along.
A friend but the same speakers with carbon fiber drivers and his sound much smoother. I just broke down and bought a set of the carbon drivers and you know my system isn't bright any more! I know this doesn't help you but I spent years and a lot of money to "smooth" out my system (bought equipment that is know to sound smooth) with our much luck and low and behold it was the speaker cone material all along.