The same 40 watts through 2X10's in a Vibrolux Reverb sounds like a dream.
If you're playing really picky venues, then sure 20 watts is about max unless the user
knows how to control their rig in any situation.
Deluxe Reverb or 18 Watt Marshall Circuit is still a ripping little kit, but you have a bit
more clean headroom than a Princeton or AC15.
I still prefer Fenders through 10's always have.
My little 21 watt Ampeg Reverberocket has been turned into the curtains to tame it
at Jammin Java.
With a strong house PA and exceptional monitoring you can make 12 or 15 watter work
but the band has to be very disciplined on stage volume.
Here caught The Pete Best Group also at Jammin Java
The guitar are both going through 15 watt Industrial Amps.
Ugly as sin, but they sounded pretty good.
Especially 15 watt amps with 2 drummers.