15' x 20' would be the absolute largest room I could hope for. I am in between houses and my last house would most likely be larger than where I'll end up (bigger city smaller house tradition). I would expect a 10' x 15' room or slightly smaller. I have two pairs of speakers that I have kept over the years: Yamaha NS-1000 and JBL 4349. The JBL's are very efficient as they have been tested to never go below 8ohms. They do require a large room because they project due to the horn. The Yamaha can manage a small room because of wall placement, but I thought it would good to have a second pair of speakers that are bookshelf if I get rid of the 4349. I'm trying to downsize, BUT IT'S TOUGH, as each piece of gear has its own special attributes, i.e. my Yamaha CX-70 has my favorite phono stage. The AsciLabs have been getting good reviews, but the seller I got the Luxman from recommend Alta speakers, so there may be other options. I would think in a reasonable room 40w class A would be enough but it's all in the circuitry......maybe Philharmonic or Kef? Thanks for some great insight more the better.