I can, though I don't usually use them like that. Even though I can be as loud as I want at home I usually keep my master vol amps around 7-ish for recording. That's super loud, way too loud for gigs, but not fully "cranked". So most of my guitar tracks with the master volume amps aren't cranked all the way, but the amps are in their happy place which is generally much too loud for bar/club gigs. That's what I consider my baseline - my own personal home recording volume that is too loud for gigs. From that level I'll do clips attenuated and turned down with the master volume. Or I can crank them if you want me too.
I tell you this, I don't know if it's technically louder by decibels, but the JCM 800 2203 is much scarier cranked up than the Plexi is. It just sounds like all hell is about to break loose. It's pants flapping powerful. I get the impression that if I'm gonna blow a speaker or break a window one day, it's gonna be from the JCM 800. It's that damn ridiculous. You know how it is, don't you have an old Ampeg V2 or something?
Sure, I can do that. Something between TV and gig volume. No problem.