Best sounding low power (under 80watts) Class AB amp?

What about an Odyssey Khartago Extreme?  Over 80 watts per channel, but not a monster.  Naim also came to mind along with Ayre.

@herman Wow! Nifty! Ever take SPL readings (with the 300B amp)?

I also suggest you look at the Musical Fidelity M5si integrated amp rated at 150wpc. Its weight is 32 pounds and it has outstanding sound quality.  Priced at $2,199.  

See link for Musical Fidelity Amplifier

"The M5si is a real high end amplifier. At 150wpc, with high current delivery, it will drive virtually any loudspeaker easily.  Internally the M5si is configured as two independent monoblocs with a separate preamp, but all mounted on one pcb. Its technical performance is about equal to the M6Si".

@herman Wow! Nifty! Ever take SPL readings (with the 300B amp)?

no, it can go louder than I would ever play it so all good there

Have you measured how loud you normally listen? What makes you think you need 80 watts? What kind of music do you normally listen to and at what volume level?

I humbly recommend you download an app something like Decibel X PRO so you can use the built in microphone on your phone to see what SPLs you are typically running. You might be surprised at how little power you're actually using...

agreed, but average listening level is only part of the story. Peaks can be much greater and that's when many speakers can use the extra headroom

From my own experience, my recommendation is a Luxman M117 integrated. It’s a classic now, but can be serviced/renewed if required.