Shortly after I acquired the amp I moved. From there all sorts of events and tragedies took priority and it took me a long time to get the living sorted and start work on the acoustics. I had been lucky with my previous homes that did not have acoustical issues I now know.
I had put the speakers in probably the most worse and wrong position first and after changing that I started to enjoy listening little by little again.

In the image you see the panels I put up against the wall, they are named 'silent lines'. Apart from being stylish, they are claimed to be of acoustical benefit. At first I put a few on strategic spots in the room, and they worked miracles. There are other solutions but with these all I have to do is unpack them and put them against the wall. Basically people will fit them on a wall but this way I can move them around or take them with me. With the reverberations brought down to acceptable levels I could start listening to music again.
(Sometimes though the massive feedback from the solid wall was an experience, if I could ignore the reverb).
I experienced the big amp as powerful. For serious listening it 'needs' to be in Class-A what makes a big difference to the sound. Basically I keep the volume regulator at 12 o'clock and adjust the volume on the Transporter.
I thought my other amp did sound a bit more subtle and a little less powerful. But I was able to get good levels of sound in my previous room of well over 50m2 or (500ft2).
About 2 months ago I put it in the system for reference. After three years it needed a break-in of a day. At lower volumes it sounded much sweeter, even to the point of me thinking it was colored. When going louder I noticed that a volume level that was good for the earlier, larger room, was insufficient for the current, smaller room. You'd think in a smaller room you need less power but not here. The same goes for the sub-woofer but I understand that for the large wavelengths not really fitting in the room.
Also when playing louder I noticed some strain, both in Class-A and AB. It is rated to do about 25 watt in Class-A and 186 watt@4 ohm in AB and switching from A to AB does not make it sound better.
While I had the other amp on, I moved around the Centaurs to try to get the best image.
After two weeks I really longed for putting back the Big Amp.
That first time listening to Big Amp again really hit me, the difference was huge! It is much more powerful, I have no figures but it has to be a lot more than the 25 watts from the former amp. I think what most counts is the delivery of current.
I listened to Helen Donath singing 'Das himmlische Leben' from Mahlers fourth symphony and it became at that moment an almost holographic experience. I guess I also was in the right mood for it.
When playing the beginning of 'Time' from the Pink Floyd album 'The Dark Side of the Moon' I experience it as being inside the clocks (they recorded actual clocks for this). This with the volume on the Transporter open and the amp at 12 o'clock.
In general listening to it I think there's nothing wrong but it could be more subtle or refined. Depending on the level of the tracks, before '12' it is a little more at ease and over '12' there can be some strain. On Mahler 4 I went to 10 past 12 and that's my limit.
I don't have too many references with high-end amplifiers. I did listen many hours to other very good speakers driven by tubes.
I am happy with it but at the same time wondering what could be a next step. I like tubes but it's got to be a hell of a tube amp for an Apogee. And you have to replace tubes. As for solid state amps there are so many I would not know where to start.