Well since no one has chimed in, I thought I'd add an update. I picked up a used Krell 300i, and still hope to get a chance to hear the Plinius, Naim XS, and a Sim i3.3 or 5.3. I'll have an opportunity to bring the Hegel H160 into the comparison in the next week or so, to add a candidate.
Comparing the three that I have heard so far (300i/i5080/Supernait 2) is a bit of a mismatch price wise, but honestly they are all great amps. The Krell and the Sim are the most similar, with the Krell having better bass and noticeably more power. When I cranked up the volume (I tend to listen very loud) on the Sim I wished it had just a little more to give with my floor standing speakers, though it was not an issue w/ bookshelf speakers or in the bedroom. The Krell solves that problem, and for not much more money, and is way easier to find. Plus I love the look of the Krell with its brushed metallic face and blue & red leds. I'd be interesting to compare the baby Sim to the Nait 5 series for a bedroom setup.
As for the Krell 300i vs Supernait 2 its a little more difficult to compare since I didn't home audition the Naim. But the obvious difference was bass and vocals. The Supernait 2's (and maybe this is a Naim trait) strength is in vocals. They seem very pronounced and sound amazingly full on the right recording. If you are into Otis Redding, Stevie Nicks, Aaron Neville etc. you'll love the sound. The SN2 couldn't touch the Krell's bass though. The other issue is the SN2 is extremely detailed, which can be both a blessing and a curse. I'm a streaming guy and use Pandora, and most of what I listen to (live rock) had me skipping over certain songs/artists and looking for better recorded material. You can tell why the SN2 is so much more expensive, the detail puts it in another league, but sadly what I usually listen to isn't in that league. Perhaps the Naim XS or even the older Supernait would be better suited for me, or Plinius or Hegel or Rega.... sigh, the quest continues, but so far the Krell has been a pleasant surprise.
