Just starting to learn

Well, I've heard that the lower-power Adcoms in that series (555-545-535) sound better, so I'd try the 545. I'd then sell whichever amp I didn't want, unless I wanted to try biamping. Biamping with those two amps should be easy, since their gain is probably identical. I don't know if your speakers have double (biwire) input connectors, though.

After that, biamped or not, I'd start upgrading with the source. I'd get the best one I could afford, then the best preamp, and so on downstream. Once I had the components I wanted I'd start tweaking with cables.

For specific recommendations, you should post what it is about your system's sound that you'd like to improve. A lot of people would be happy with the gear you have and wouldn't see the need for any upgrades. Maybe that includes you.

Regarding the two preamps, if you'll have the Adcom back soon, just compare it to the Carver for yourself. Another idea, sell both and buy a nice used tube preamp for around $1K. Yet another idea, sell the Carver and send the Adcom to John Hillig, of Musical Concepts, for modification & upgrade.

I had an Adcom 535 in the attic, doing nothing. I sent it to John Hillig, for the LX-Signature mod, and it now sounds totally kickass. His mods for your Adcom preamp look very interesting and may be a very cost effective upgrade.

If everything sounds enjoyable, buy more music.