Welp. I went and did it. In a huge rarity for me, I not only bought a piece of gear brand new, but I did it practically on a whim. A friend of mine who is a professional jazz guitarist posted on Facebook, raving about this new 50w Boss amp he'd gotten and how it was the best small gig amp he'd ever owned. He had put his Quilter and his small Fenders on the shelf. And the best part: it was $199 brand new!
I had never heard of these amps at this point.
I went and played the Katana 50 at Guitar Center, and it really impressed me. But I wanted to buy it through a locally owned shop, where they were backordered. While I waited, I realized that the 100w combo had a number of features the 50w lacked, including the effects loops, the line out, the presence control, and (most importantly) the ability to use the Roland 5-button foot switch. So when the local shop sent me a message saying they had gotten the 100w in but the 50w was still in transit, I sprung for it. $329, still dead cheap for an amp this good. And it is good. I'm seriously blown away!
The clean channel is superb and takes pedals really well. The onboard effects are quite good, and I'm looking forward to connecting it to the software and seeing what the other 50 effects can do. The acoustic amp sounds quite solid and will be useable when I can't run direct at acoustic gigs. And the power attenuation works mint—it sounds great at every level, from 0.5w bedroom volume all the way up to 100w ear-crushing volume.