I've got a Fender Stage 185 with low power overall on both channels.  It sounds OK and doesn't crackle or hum, just doesn't get NEAR as loud as it should.  I would suspect something in the power section since it happens on both channels.  I would guess Q17 - 20...  am I on the right track?

schematic attached.
Any idea how to narrow this down anyone?  I'm a tube guy so this SS stuff is a little new to me.

thanks in advance!