In general I find preamps make a bigger absolute difference in overall sound in my system than amps. But one area where I find amps make relatively more of a difference is with regard to bass, which seems to be high on your list of priorities. The quickest, tightest bass I've had in my system came courtesy of Bryston amps, and if you're looking for air and separation their preamps are way, way up there too. I would think going with something like a BP-6 would be a huge improvement (i.e. wider/deeper 3D soundstage, increased clarity/detail and sense of space, etc.) over your Carver's preamp section, but you might have to stretch your budget a bit. Of course the 20-yr. warranty is also nice to have if you're a buy-and-hold type guy.
You also seem like a good candidate for adding a quality subwoofer at some point. If you're looking for something that would provide a big absolute difference in what you're hearing across the board, there you go. Hope this helped, and best of luck.
You also seem like a good candidate for adding a quality subwoofer at some point. If you're looking for something that would provide a big absolute difference in what you're hearing across the board, there you go. Hope this helped, and best of luck.