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

This is very difficult as you are looking for low weight in a class where transformers tend to still be relatively hefty.  And…what sounds “good” to you.  Do you like a more liquid, musical sound like Luxman or do you prefer a more clinical and accurate sound like Hegel?  
 

Chord comes to mind if you like a more accurate sound.  The TToby and etude are good sounding amps.  I think they are class G technically.  For a more liquid sound, I know this is class D but not your Class D of 10 years ago, check out the AGD Audions.  You can easily mistake these tiny little amps for MOSFET based ABs.  
 

Full disclosure, I am a dealer for both brands but am struggling to think of any items that meet these requirements.  I think Valvet is class A.  Sugden is class A.  CANOR, NAD, Benchmark, etc… are all Class D.  This is a tough request

Ayre Acoustics AX-7E, hands down great amplifier.

Ahh sorry missed the class ab bit of your post. 

How about a Schiit Vidar? At 100 watts/ch, it is a shade more powerful than your 80 watt spec, but definitely class AB and 22 lbs and a fairly small footprint.  (In my case, I have their class A Aegir which is much lower power, but all of their amps have excellent sound quality.)

+2 On the Schiit Vidar 2 amp

Mike

https://www.schiit.com/products/vidar2