I think the OP is actually asking about the new expanded Rega compared to the old small Rega- Rega QC before they increased their number of products from a handful to a stable, and took their markets worldwide.... and anybody that might have been along for the whole ride, or most of it, what observations they might have. I mean how would you notice a slip without some frame of reference?
I'd say there is some truth here. I'd also say that newer does not mean better, especially when reliability is concerned. I just told my HVAC guy my AC system has worked for 25 years, he said if I get a newer system expect 15 years tops, and that he does'nt like it, but that's just how it is. Quality/reliability of just about everything has slipped if you ask me.
I have owned lots and lots of Rega gear for a long time, I've had some issues with certain products. The cdp's apollo/saturn mainly, but other things too. Overall I do believe there have been some slip ups QC wise on some of the newish stuff. On other things like a slight hum coming from the motor housing of TT's that have the TTPSU, that's just Rega (not the speakers, the motor itself, if you have hum from speakers that is either a turntable placement issue or a cartridge issue- either the cartridge is not grounded right or not shielded well, and by the way Rega cartridges seem to have little if any shielding, they don't hum as much as unshielded grados, but they do hum a bit) .
The Brio circuit is more like a tube circuit and like a tube amp it does in fact seem more prone to hiss, and also RFI pickup than their other amplifier designs. Neither thing seems to get in the way of musicality. I have to say my RS3 drivers are fine, I play loud sometimes but not really loud, the RS3 drivers are also quite small size wise and I would'nt expect them to do concert or disco sound levels without blowing. I did blow my Polk audio monitor 7 speakers many times- they always sent me new ones, eventhough I now know any speaker would have blown the way I used them back in college. Likewise Rega has always addressed any problems, so no worries, but yea I feel there is some truth in the OP's statement and it's not just Rega. That said, I love their stuff, I love the company, I love the sound, I am a die hard fan. And I disagree with those who say people only post on the internet when equipment has a problem. On this very site I chime in with my positive impressions of gear in the comment section for reviews on the Rega Elicit, and The Rega Exact. I very favorably review the jupiter cdp and the RS3 speaker on audioreview.com.
It should also be said that as far as I can tell, other than your DAC issue (which may be it is'nt holding a lock for whatever reason), your stuff works when you put music on. The things you mention with the brio amp and the turntable are cursory traits of the gear that a replacement would probably also have..... do you hear a motor hum or amp hiss when listening to music?