Update - Didn't get to turn it up, but did switch the impedance (back) from 8 to 16 this AM before work. In the meantime, my google results regarding whether a mis-match could make that much volume difference were between '16 ohm speakers into an 8 ohm amp will be half power' and 'there should only be a mid-shift from a mis-match on a tube amp and no volume drop.'
Between those two statements, I could believe 'half-power' - After flipping the switch to 16 it's where I figured it should be - can't turn any channel volume beyond one for a listening-level/good neighbor sound with the master dimed.
(On first try getting it home I was worried I'd broken something, and pretty alarmed aka scared the volume knob was tipped so high, without blowing my ears off. Made me assume I wasn't getting a full signal for the guitar, and that if something shifted and I all of a sudden got full output, I could blow up the house. Though still playing at bedroom levels for now, I didn't think the amp sounded any better at 8 ohms so leaving it at 16 .)
Reading up on the speakers (nope, no plans to replace) sounds like varied feedback depending on open/closed cab. I have Celestion Rocket 50s wired to my 100 watt Fender Libra; I may plug them in momentarily for a laugh (curious if they make me appreciate the stock speakers more, or I may actually like them knowing me.) Overall really enjoying it; I don't hate the high gain channel (much better without mid-scoop engaged,) like the clean channel (actually *do* like it with the 'deep' switch, sounds like every recorded clean guitar in 2002 ) and the crunch channel is good - but I'm actually glad to have the higher gain channel as well.
King Buzzo: I love when people come up to me and say “Your guitar sound was better on Stoner Witch, when you used a Les Paul. “...I used a Fender Mustang reissue on that, dumbass!