Really helpful and thoughtful posts @goldenways and @996turbo911 (nice car too!). Thank you.
And of course you are right, @goldenways about the ratio of potential listening hours to those at play for return shipping. I was just being honest about my behavior and that the hassle of the return would quite possibly influence my sense of how much i liked the amps once i had them installed. I could see convincing myself that it was a big improvement and worth keeping them. I might have a chance of being more neutral if I could audition a few different options in person, or even better with a local dealer who would help me with an in home try out, because for sure hearing it in my space with my speakers is not something that can be recreated at an audio show or a dealer’s showroom.
And @996turbo911 , fair question about Class D. I am not 100% committed to class D; it’s more that after a lifetime with AB amps — the last 11+ years with the perfectly fine Parasound A21 with the P5 preamp — I am enjoying the M33’s sound and sure don’t mind that it is a lot lighter and runs cooler. But ultimately, it is as many of you have said, I should really find a way to listen to more equipment. As it has only been recently that I’ve had a lot of time to just be at home and listen to music, I was content with my Parasounds driving a pair of KEF R500s; so it’s just been that past year or so that I’ve really been focused on upgrading components to get even better, more life-like, more dynamic sound. I probably should just chill a bit and live with the M33 and the Epicons and the C399 and the Revels (they’ve only been with me for a few weeks!) and see if upgrades make sense. The piece that is limiting from a pure performance perspective is that, even with help from Roon support, I have been having trouble getting Roon to be stable when playing in groups that mix WiFi and Ethernet wired components, despite putting my Roon server and the audio equipment on their own fiber based network (with most of it direct Ethernet connected); and that means, if i have to drop Roon, i am limited to BlueSound connectivity if I want to continue to have multi-room listening options, and given the way our home is constructed, and the way we live, that is pretty crucial.
All that said, there is a used Jeff Rowland 625 2s power amp at a nearby dealer in great shape at a pretty tempting price and I will ask them to hook it up for me to hear, but then I run into the question of what pre-amp; given my BlueSound issue, would a new or used NAD M66 (i would trade in the c399 toward such a purchase) be the way to go, or do i need to look elsewhere and figure out my multi-room issues after I’ve settled on the amp/pre-amp/streamer/DAC situation. I am really resistant to the idea of getting DAC/Streamer separate from each other and even separate from the pre-amp. (I would even consider going the other way and skipping the pre-amp altogether by hooking up an amp directly to something like the Bluesound Icon, but that is probably heresy?)