I suspect improvements will be very small and no reason to change from a 1st to a 2nd generation Purifi amp, but if moving from another Class D (or any other technology), it is probably best to look for a Purifi amp with a 2nd generation board.
Much bigger differences are likely according to the implementation of Purifi. There are lots of "garage-built" Purifi amps that use the cheap Eval(uation) board, whereas others such as NAD and T+A build under license after authorised tweaks to maximise performance and the use of superior additional components such as power supply. Just look inside these amps to see the difference in power supply, RFI-protection measures, etc. Not all Purifi amps sound the same!
I see that the Benchmark AHB2 is top of your graph. This is just about the dullest (though probably most accurate) amp that I've ever owned. Choosing an amp based on SINAD is frankly daft if you want one that provides a degree of excitement approaching a live performance.
Looks like he's saying the Benchmark sounds fantastic on good material but he doesn't like it for bad program material. All I can say is that I've had euphonically-colored tube amps in the past, and I always ended up replacing them because they were getting between me and the music. I like revealing and neutral.
Anyway, I've AB'd the Benchmark with e.g. my A-21. The Benchmark was a bit more neutral -- better in the highs and neutral in the midbass, while the A-21 seems a bit warm there -- but it wasn't as good on piano (go figure). But the differences were subtle.
> I was proving that the same amp board (apples-2-apples comparison) can be worsened by expensive inhouse subjective "improvements"
If you think a Purifi amp based on the cheap Eval board will reproduce music better than a Purifi NAD M Series or T+A, I guess you have never compared them.
