Would switching amps make a big difference?

I used to own Rogue equipment

I also had a pair of big Rogue M180 monoblocks here for a while for repair, I put them on my ML esl’s they sounded OK, but couldn’t match the solid state for tight drive and extension in the highs, even on the 4ohm tap.

Cheers George

I think you would achieve much more bang for the buck by changing out your preamplifier. Give the deHavilland UltraVerve a shot, at the very least you will have a preamplifier you can keep for life. I have spent time with your current preamp and with the UltraVerve so not speaking out  of school. Below is my room at the show. 

“Though I've heard the Wilson-Benesch Curve floorstanders many times before, I found that they sounded spectacularly good as driven by Kara Chaffee's amazing deHavilland tube electronics . Nothing I heard at RMAF, save perhaps for the far more expensive Vandersteen/ARC system, could touch this rig for sheer midrange purity, detail, three-dimensionality ." Chris Martens TAS on the 2009 show.

Wow, I've gotten a ton of useful ideas here to my question and am thinking of starting with the Zero-Autotransformers which should solve the Martin-Logan / amp speaker compatibility issue.

Next question is, if I were to replace my admittedly old Belles 21a preamp - thoughts on the following 4 preamps?
> deHavilland UltraVerve 
> Backert Labs Rumba 
> Don Sachs 
> Linear Tube Audio

Of the list above I would do the Sachs or deHavilland. The Backert Labs is an excellent preamp; IIRC it employs an output transformer. Since your amp is single-ended input I don't see an advantage with that. I also have a preference for 6SN7s as a line stage tube- to me they are more robust and musical than 6922s/6DJ8s or any of the 12A*7 series (we use the 6SN7 in the line section of all our preamps); that is how I arrived at this opinion.

@cdc2 the zeroes would be a quick fix for your specific case, down the road if that's an option and IMO I would replace the speakers by something more friendly impedance wise to your gear. Only my opinion.