" mb1audio - thanks for the listings. A lot of older power amps but I don't think Class A/AB has advanced much in the 21st Century. "
I'm not sure I Get your post because you're asking for A/B amps. I've heard all of those amps, and owned some of them. They sound nothing like each other, or an A23. For example, most people would take a McCormack DNA-125 for $900 over any receiver on the market and the A23. Technology is one thing, haveing the skills to implement it is something else entirely. Nelson Pass, CJ and YBA are made by companies that help define what state of the art is.
That said, my recommendations were made in error. I didn't realize that you intended to keep the AVR as a preamp long term. I assumed you would be looking to upgrade to a preamp similar quality. It still makes sense to upgrade the amp because more power usually is usually a smart move. But without a matching preamp, you'll never hear what the amp can really do. A much better fit for your goals and equipment would be something like Emotiva. You'll get the extra power that you need, but you won't be wasting money on more expensive products that your system won't be able to take advantage of.