I got a new Pro Stock B+ 6 weeks ago. I gig hard rock. Splawn recommended the PS over the Compy and SR. when I first got it, I was worried: it is loud at 9:00. Then I spent a few weeks with it and now I love it! The Loop Volume does work very well!! The loop volume won't get the power tube saturation going as much, but the Splawns have more than enough gain for metal. You don't need a boost for all kinds of metal, but you might like boost for variety. The on board boost works well (OD1/2) and it adds a touch of boost, but not a ton; however, you don't it. It's Marshall metal and then some. I get great Tool and AIC tones out of mine.
Mine was a little noisy at first, but it settled after a few hours of play. They are pretty quiet amps.
I don't use clean channels. All my tube amps clean up well with the guitar volume, so I would give the 50w QR or Compy a look. But I have no regrets going with the PS, and I too was worried about these amps sweet spot being too loud. I gig, so it's really great.
If I was more of bedroom player, I'd look at something in the 50w range for Splawn.