Replace my Berning ZH-270?

Music Reference RM9 works well (I have the at setup with your speakers)
The Pass XA30.5 worked very, very well for SS.
CAT JL2 (which I also own) is about as good as it gets wiht the Merlins and just about anything else.
I think you would also do well with an Amp from VAC or Manley.
And of course a Joule ot Atmasphere OTL.

You could purchase Pubul57's CAT.

Just out of curiousity, what is the problem with the 270? Your description of fast, open, transparent, tight bass sounds like the 270. What about trying for a second 270 and monoblocking them?

I would agree with Oneprof that your prerequisites sound exactly like what the Berning does best.

I've never heard the big CAT amp but, for the price, I would expect it to do very well. I have had the M60 atma amps and heard the MA1's and VTL 450's (latest version is very nice) but for the price, weight, heat, and sonics the Berning is very hard to beat.

The bass on the Berning would rival most on the list above.

Enjoy the chase, I switch between the 110lb Wyetech Topaz and 10lb Berning, each has its own attributes.

Nkj

There is a thread somewhere by SBank who made the move from Berning to Atmasphere. I think that thread pretty well covers the pluses and minuses of the Berning versus some of the obvious candidates (CAT, Joule, and Atmasphere)for working well with the Merlins. On ergonomics alone (not meant in any way to diminish its sonic achievements) the Berning is the easiest way to own a tube amp with minimal fuss and bother. I do think that you will find a move to one of the three amps mentioned and sonic step forward. Of course I know nothing of the new mega-buck Berning, that too may be a consideration.