Joe, have you tried any tone adjustments or does your receiver have any type of setup routine for distance or level matching? If you have sufficient power now and it gets loud enough without distorting, a different amp won't change anything.
As it is we don't really have enough info to be any help. What equipment are you using, which receiver and preamp? What speakers? Size room? How far do you sit from the speakers? Do you use any dsp or room correction? How are your speakers placed in the room? Close to any walls? How far apart? Are your tweeters at ear level? There are a lot of factors.
