A new amplifier can't solve the problem(you might want one for different reasons, but that's beside the point). Using the treble tone control can help, or the different treble curves that some processing, such as Audyssey, has available. A "warm" sounding amplifier would be either incompetently designed or defective; an amplifier should have no "sound".
HAHAH, John.. You should have heard the response i got when i was buying a preamp for my turn table.. The guy on the phone said well, brand X has a very warm sound... So i asked him "would you quantify warm please"... to which he stumbled for a minute or so and finally came up with... Well, brand X is a better built product that uses better components....
