Your setup is well balanced. I don't understand why you want to change out
the amp. Is there something wrong with it? IMHO, I don't think the amps on
your list are better than the MC2105. They sound different, yes; but not
necessary better.
If you get tired of your amp and want a different sound, that is fine. But than
you need to audition them yourself and decide what you like best. Buying
something based on other people's taste will probably end up with
disappointment, especially you already have a well matched system from what
I see.