In your system, the pre, amp, and definitives are pretty level in quality. Changing the amps or the speakers, i think, would make sense. The pre and source units are good enough where they could hang around as you replace the amps and speakers. You could get a mid to early 1990s amp from a high end manufacturer which would be a big improvement. I had an NAD amp that i replaced with a classe audio 70 ($400 used), and found that the classe was much, much better, in every way for not much more money. Just an example.
Are Carver amps worth a damn?
i have a system which I use for both home theatre (70%) and for music. It is comprised of a Theta data basic transport, a Nakamashi cr-2 tape deck, a Marantz AV-550 preamp /tuner, a panasonic dvd player and a proscan vcr. For amplification I have been using 2 Carver TFM-35's and a TFM-15 for the surrounds. I have an unpowered sub so I get 1 channel of 250w to the front 3 and the sub, and 100wpc to the surrounds. For speakers I am using Definitives all the way around. Are the amps my current weak link in this system?