I'm by no means a Levinson expert, but I understand the No. 23.5 to be a very fine used amp. You don't seem many of them for sale though, and usually they go fast when they come up. I always consider that to be a good sign when considering used gear.
BTW, I have a No. 23 that I'm pleased with...
BTW, I have a No. 23 that I'm pleased with...