Requesting opinions about 4 specific amplifiers

I suggest you forget separates and consider the darTZeel CTH 8550 especially if you like the form factor of integrated design.  From inputs, including the world class phono stage to the outputs everything is designed to maximize purity and deliver rich music with full dynamics and  clarity.  I have churned a lot of equipment over the years and when I got the CTH 8550 I was amazed as it outperformed all the separates I'd tried including the AR reference 6 pre amp and 610T power amps, Pass Labs and so forth.  darTZeel is expensive but if you off load what you have and combine it with your budget the difference should be manageable.  The Sound Advocate did a great review including interviews with Harv Delétraz you will find interesting.  Good luck.  

British Audiophile loved Atoll integrated - in300  @ $4500 new.  tilts warm with good bass control.  For amp only, Atoll has am300 for $3900 new.  Mos-fet designs, so tend to be slightly warmer. 

Aesthetix is a brand I sold for years and still has outstanding integrity ,they

wind their own transformers and enclose them in a faraday type cage to contain any magnetic fields , they build a quality product 

even their integrated Mimas has a Hybrid Vacuum tube preamp section .

Coda too has Some nice products in their upper line ,who btw we’re Pass labs engineers before Pass went independant.

your speakers are what model and effficiency ? Very important to know.

i have  40+ years building system synergy .I owned $6 figure Audio systems 

but technologies have moved on even class D look at AAvic from 

Audio group Denmark ,they have great newer technologies ,in part using multiples 

of Tesla coils to dramatically lower noise floor and many other things .

I myself am looking to upgrade but not until our home additions are completed 

being married means Audio is not 1st ,since I no longer own a Audio store .

Why not just get a Buckeye Purifi. Objectivity better than any you've listed.

You listen at about the same levels as I do but I don't consider it loud. Church is that loud.