Have been A\B testing Aethos v Supernait 3 (SN3).
My setup is: Rega P6, Dynavector20x2l, Aria phonostage, Chord Shawline interconnects/ mains/speaker cables. Buchardt S400's bookshelves (which are incredible BTW if you're tight on space).. Rega Elex-r, Apollo CD. Bluesound Node2i (Tidal/Qobuz Studio). So after hours of full on A/B'ing here's my humble opinion.
Overall I found the Rega Aethos sound more engaging, richer and detailed. It sounded great at low vols, this was a big surprise as my Buchardts prefer higher vols but the detail and control at lower vols is really enjoyable and if you crank up the vol I could actually play at higher vols because of the control the Aethos has. My S400's are 4ohm and sound incredible with the Aethos. I liked the volume control, I thought incrementally it's spot on. I noted that the balance between the 2 speakers was better, more equal if that makes sense...
I understand the Naim PRaT thing now but the Aethos is no slouch... I like relaxed listening and found the SN a little dry and thin sounding, it's hard to properly verbalise. When it comes to Vinyl the Aethos dug out a little more detail than the SN and sounded richer again, fuller somehow.
To balance this out the SN is lighter where bass is concerned but it finds it and controls it better than the Aethos. SN has more grip on the bass but I missed the low end that the SN couldn't quite reach, the Aethos. Surprisingly the Rega Apollo CD sounded great with the SN!! they really complimented one another. The SN also reminded me of the Hegel H390 which is a huge compliment because that Hegel is a cracking amp, I loved it but... Bang for buck I'd get more from the Aethos personally.
Soundstage was a tie but Rega edges it with depth, in one review its mentioned a 'walk in' depth & I hear that. The SN was slightly more detailed in the highs on some tracks. Johnny Cash's Hurt for example but the Aethos gave his voice more texture, realness.
The SN vocals generally are more forward sounding. I didn't have time to test the headphones amps. Conclusion : I love my Elex-r but the Aethos definately gives more controlled power, detail and textured layers of sound. Having plugged the Elex back in I notice a huge difference...
Once I eventually realised it really does come down to 'what sound do you prefer'... it was a relief and I chose Rega...the SN just isn't as much fun to listen too...