Using your Pioneer as a pre, I doubt that a new amp will provide a "significant improvement" in SQ. Perhaps an obvious improvement, but not necessarily significant. As @spark1 mentioned, a more obvious, and perhaps significant, improvement would be a better preamp.
A while back, I replaced my B&K ex4420 with a Sansui AU-919 (amp portion only) because, at the time, I needed to run 2 sets of speakers (not at the same time though). The difference in SQ was definitely obvious, but a much more significant improvement came when I replaced the preamp.
Personally, I'd start with a new preamp, and then at some point, upgrade to a better amp. The pre that I'm using is a Zero Zone, China made knockoff (ebay), that blows my Schiit Saga out of the water. The difference between the two is obviously significant.
A while back, I replaced my B&K ex4420 with a Sansui AU-919 (amp portion only) because, at the time, I needed to run 2 sets of speakers (not at the same time though). The difference in SQ was definitely obvious, but a much more significant improvement came when I replaced the preamp.
Personally, I'd start with a new preamp, and then at some point, upgrade to a better amp. The pre that I'm using is a Zero Zone, China made knockoff (ebay), that blows my Schiit Saga out of the water. The difference between the two is obviously significant.
