T+A Class D Amps ( M200 or A200)?

Totally appreciate that, thank you, @soix.   I do expect they would both be pretty sonically neutral. The other item on the scale in the M66’s favor (for me) is Bluesound. Probably not worth 3K on its own, though.  But if I were to go through with this, I would hope to do a bit better on price of the M66 via the used market or through “kindly” dealer trade-in concessions.

Thanks, @ericrhodes1 

you have articulated the reasons for my hesitation pretty well. Will the T+A sound better than the M33 in any material way if i am not upgrading anything else?  For a lot less $ i could trade in the c399 for a new m33 v2 to be used for the Epicons and put the OG m33 with the Revel 226Bes. 

All good points, thank you guys.

and @soix, you are right I would be pretty much throwing darts in a very dimly lit room at this point. I should figure out a way to go and hear more gear before i start buying stuff (even if it is returnable). The hassle factor in return shipping decreases the incentive to be strict about whether the item really is a meaningful upgrade. (That, plus placebo effect and confirmation bias.)

@soix, thanks for that advice. Both AGD and Tempo have escaped my radar. I would be happy to spend less!

To answer your question, the Characteristics I’d like are, very generally, to keep the neutrality of the M33 but if possible add a touch more oomph (for lack of a better descriptor), even though the M33 is 200 watts per channel at 8 ohms, there is something about the 6 ohm & 88dbs sensitivity Epicons that makes me feel like they could use some more power and I am purely guessing  that the higher voltage T+A s might create a bit more crispness across all frequencies, without moving into harshness or sterility. 

Thanks, @soix.

I had my concerns about that, but figured i might try it initially while i search for an alternative. I am also wrong about the nominal impedance of the Epicon 6s; it is 5 ohms not 6; even more of a concern about power/voltage.

@soix, thank you for trying to put your intuition and experience to work translating my inarticulate resort to “oomph” as being what I am missing.  I think though, I’m not as negative on the M33 as you suspect. I don’t think of the sound currently as anemic or thin, but it could be described as a touch too polite. So that is in line with your lacking ‘life/emotion” and “heft” concepts. Tonal density and color seem very good to me and I would say overall I am about 90% happy with the sound the speakers make. It is just a touch of crispness and maybe even authority lacking on the bass (say when a drum kick happens) and similarly on high treble like when a triangle is struck in a passage (flutes however sound great). (The M33 is also driving a REL T9/x sub.). Violins, Cellos and trumpets & sax all sound great; resonant and controlled. (Clarinet & piano sound especially good: clear, natural. Very much a “you are there” sort of experience. I certainly don’t want, you are right, harness or over brightness or any thing that could be described as “aggressive”.

I started down this path not because i am all that unhappy with the Epicon 6/M33 combo, but because I feel that the 226Bes deserve a fuller sound than the C399 is giving them. (Here one gets closer to missing life/emotion, while still not being anemic.)

The C399 has the same DAC and streamer technology that the M33 has, but an inferior (while still perfectly solid mid-Fi) amplifier.  I have often heard of the M33 referred to as mid-Fi, and maybe it is — the upper end of mid-FI perhaps? — but the C399 amp is more so. I think the M33’s coloring (mild as it is) and polish and its better bass control and clearer, more shimmery high frequencies would improve how the 226Bes sound. (Fortunately, at least the C399 does not bring out any shrillness or over assertiveness in those Beryllium tweeters.) The 226Bes are easier to drive than the Epicons:  8 ohms nominal impedance and 90 dB sensitivity (at 2.83 volts at 1meter); so, that also made me think that the M33 might shine more with them.

And all of that is what lead me to thinking about the T+A M200s — same very good amp technology as the M33, but with some the fancier, better high voltage input stage and proprietary power supply. (And just the potential benefit that separation of the amps into 2 mono blocks offers.) And same watts per channel.

Hope that helps some.

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?)

Thanks @prophet9 and @goodlistening64 ; very helpful to me.

  @soix, do you think, cost aside, that the eversolo dump-a10 is likely better than the NAD M66. The M66 has also gotten great reviews (e.g., https://www.stereophile.com/content/nad-m66-streaming-preamplifier-measurements-page-2 )

 and has more functions than I will ever use. Pretty solid customer support room, at least based on their being very helpful when i had some very boneheaded questions when setting up the M33.

I’m surprised that nobody has weighed on the merits or concerns raised by the idea of going with the Jeff Rowland 625 S2 (whether with the Eversolo A10 or the NAD M66 or with some other solid state pre-amp)….