Fair enough. I'm always very sceptical of anything audio related as very few people seem to do objective testing.vit often comes with words which sound very BS. Fwiw I've never needed more power and I'm using denon w2200 in a reasonablely large room (although my hearing is fantastic so don't need to go that loud). How do you know what's in each amp (I'm think of av) as the spec sheets tend not to show much detail.
Some of it you'll get from the spec' on the manufacturer's web site. Stuff such as better room EQ, so Audyssey MultEQ / MultEQ XT / MultEQ XT32 would be easy to pick up. How they compare to say the different iterations of other room correction systems such as Yamaha YPAO/YPAO R.S.C., Dirac/Dirac-Live, Pioneer MCACC / Advanced MCACC / MCACC Pro, Sony DCAC, Meridian Room EQ etc requires some reading.
Other difference will be buried away or might require some extensive searching and reading between the lines. For example, Pioneer switched to 'digital' amplification in their AV receiver range - because
digital is better, right?
Well, done right it can be very good. If you've heard Bel Canto or David Berning gear then you'll have first hand experience of how SMPS-based amps can be made to sound very good indeed... at a price. Some of the Rotel multichannel power amps went the same way, but now they're switching- or have switched back to analogue, I believe. Classe has been doing Class-D amps for a while.
Class-D does offer some advantages over analogue since it's chopping up the direct mains supply rather than storing a chunk of charge in some capacitors. In very basic terms your class-D amp is effectively wired direct to the power station, and so the current delivery can be very large. Sonos amps run on class-D, and they'll comfortably run a 4 Ohm load whereas a similarly-priced conventional analogue amp might baulk. The difference though is in the fidelity of the signal.
Where class-D is used primarily for its cost/space/weight/energy savings, or to offer a bigger wattage than is possible with a conventional analogue amp, then it's easy for the sound quality to take a bath. It's hard to shake that image, and so going class-D is a bit of a gamble. Yamaha has gone class-D with its new RX-V range, and of course we've all been listening to class-D amps in sound bars, iPod docks, smart speakers and probably car audio for longer than we realise.
The key to all of this "what's inside?" malarkey is reading and research.