Will a new Preamp sovle my Problem?

You could try a little experiment. I am assuming that your listening position is somewhere greater than 6 feet from the speakers. Set your volume control to where it definitely sounds bright. Now move to within 3 feet of your speakers. It will be louder - but, if it no longer sounds bright , then you definitely have a room acoustic problem that can be fixed without a lot of $$. If it sounds louder and still sounds bright, then room acoustic changes are probably not going to completely solve your problem. If that is the case then either a "muddy" tube preamp will likely help but will probably leave you unhappy with the low frequency sound also. Biamping may help - but that is no so easy to do and get right just by going by ear. Attenutate the high frequencies either via a treble control or with filtering. By the way - I would not worry about tinnitus do to the brightness - tinnitus results from the sound wave - not the sound of the wave. The largest population with tinntus is that of combat veterans - particularly those who served in artillery units. Fairly low frequencies but massive wave fronts. It is the sound pressure that does the damage - actually distortion is likely to cause you to turn it down and prevent tinnitus - the quickest route to tinnitus is to listen to distortionless pleasant music at high spl's because you won't turn it down. A friend who is an audiologist tells me that the little in the ear canal earphones everyone uses with their ipods is about the most dangerous way to go to damage your hearing. His explanation is that the tightness of the earphone leaves no avenue for dispersion of the sound wave - it does not get dissipated - it just hits the hearing mechanisms - he predicts that there will be a rash of hearing problems directly attributed to those little gems. Fortunately, audiophiles are not big on the Ipod and earbuds.