To my knowledge Rotel is using class d for a long time in their AVRs.
As for TPA-3251 there are 3 of these in HEOS AVR 5.1 that was released in 2017. It was a complete redesign of an AVR. I have one and I am very happy with it. It is powered with separate SMPS power lines for AMP, network and preamp. Sadly it doesn't have any room correction aparat from manual settings. It was also quite expensive on release about 900EUR. It can be bought for third of this price now second hand.
I think there is little market for it. I would say younger people tend to get integrated streaming devices, either active speakers (bar + sub, rarelly satelites) which are already built around class-d or little streaming integrated stereos.
Older, who still wants big AVRs, still belive that it must be class A/B and it must have big heavy transformer for proper power (no SMPS).
I think I qualify for the Older category, having first become interested in HiFi in the late 70's....
I am power amp class agnostic... (I would categorise a whole swathe of designs as "AB' including the G, H and current dumping designs) - I have even heard excellent class B designs, and currently use Class D for my mains.
I would completely separate the power amp class from the power supply type, in fact, I think better value for money could be achieved, with high current capability from using SMPS with traditional Class AB amp section.
My real concern with SMPS and Class D, is that when compared with some (not all) AB designs, Class D and SMPS designs are basically un-repairable, and depend on replacement of entire board assemblies, rather than being able to replace individual components if and when they age/fail. (perhaps this is where I show my age)
For that reason I have a very high regard for the designs of Peter Walker (Quad) - his current dumping amp designs, were always designed with an eye to maintenance/repairability, resulting in classics like the 606/707/909 being high performing even up against todays designs, while being ecomonically repairable, and very long lived. (refurb every 30 years seems to do the job!)
Having said that, AVR's today are highly complex beasts, with a relatively short lifespan (in terms of features/functions and redundancy due to codec and standards redundancy/progress) - sadly, after a fairly brief period... 5 to 10 years, an AVR (or AVP) becomes obsolete. (eg: you cannot decode Atmos on a 10 year old AVR, nor does it support HDMI 2.1, etc...)
The "front end" or AVP parts of a setup, including streamer, HDMI switching, DSP, and to a lesser degree DAC, become obsolete very quickly - whereas the power amps, well a Quad 606 from the early 1980's is an excellent power amp today, over 40 years later.
It's nice to have a fully integrated AVR, with beefy amps, and everything onboard - but it involves a lot of stuff getting thrown out every 5 years.... having said that, it is often more economical to get an AVR with pre-outs, and connect external amps, than to get an AVP... due to economies of scale! So you will find people using internal amps for less demanding height/surround speakers, and sometime decades old power amps, that have been through generations of AVP's/AVR's powering the main speakers.
Getting back on topic - it's not about Class AB vs Class D - at the quality end of the market, either topology can do the job well, and efficiently.... other factors are more important.
