What Integrated Amp do You use

Krell K300i here, with Monitor Audio PL300 II’s.

Bryston B135 Cubed.  It's an amazing sounding unit!

Esoteric F-05.  Purchased it after realizing that a Rega Elicit R I purchased, while an excellent product simply didn't have the muscle to drive my ATC 19 v2'  properly.  While on paper the amplifiers have sort of similar power ratings the Esoteric takes the ATC' from a whisper to utterly explosive levels with a clarity that' just on another level from my Rega.  Very Happy with it.

darTZeel CTH-8550 integrated amplifier

If you can afford a new one buy it, if you find a used one buy it, you will never look back.  With integrated MC phono, you may never consider separates again.  

ML 585.5 here.  Got a screaming deal on a new unit and pulled the trigger. Didn't have a chance to compare to others, figured it was in the top of the range I'd be looking at and would make it work.  Paired it with a pair of Devore Gibbon X's and have been extremely pleased. Speakers were powered by a class A amp previously and really didn't shine.  Oh how a little power changed that tune. System is a bit warm but that is probably my cables which are legacy, known to be warm and due for replacement next.  The other amp I really wanted to try was the Luxman 590, which I still hope to test someday.