Yes, Zaphod, that's entirely reasonable. First, whatever power amp you use, make sure it's bridgeable to 8 ohms, because there aren't that many 4 ohm cabs out there. Second, consider that the same rig may be useful in the studio, but... the problem is that big power amps usually have fans, which make annoying noise in the studio. Amps with cooling fins are excellent, but usually have much lower output. You can use any guitar cab- after all, it's a guitar, right, and produces a certain spectrum of sound. You are right, of course, that guitar cabs tend to have a little more character. If you are plugging the power amp into a guitar cab, use "live" mode, which disables the cab model. If you are using more broad spectrum speakers, sich as PA speakers, use "studio" mode, which engages the cab model. For more broad spectrum applications, acoustic amps work very well.
As far as specific pieces of gear, I can only recommend the ones that have worked for me. In the studio, I use a Carver PM125 power amp (no hum, no fan) into a Marshall 1X12 with a Celestion vintage 30 (live mode) or a Fender 1X10 wedge monitor (studio mode). Occasionally I plug the POD straight into an M-Audio SBX subwoofer and 1 M-Audio SP5B and mic up the monitors (studio mode). Put the mic right in the near field, and use the best condenser you have. Listen through cans. It'll sound like shit everywhere in the room except right in the near field, where the mic should be.
Live, I've had my best luck with acoustic amps and small PA's. I usually use a Fender PD250 Passport. For really small solo gigs, where I switch back and forth between acoustic and electric, I use the Passport for vocals also. OK, a 250 watt PA is pretty weak for a band, but if you think of it as a 250 watt acoustic guitar amp with 2 cabs, it's got plenty of balls. My friend on the Left coast, Maureen Fleming, does the same thing with an
SWR California Blonde, which I have used and it worked just fine. I usualy use a VAMP II live, because I don't own
a floor POD, and I can't be bothered hauling the POD Pro around. On stage, the Carver power amp runs the Fender wedge monitor off of the tape out from the Passport, so I get to have a monitor (woo hoo). I'm not that rich, so a lot of this gear does double duty, on stage, and in the studio. Another option is to run one or two Eons or similar powered PA enclosures right off the POD. For REALLY big gigs, rather than going straight into the board, I will actually mic up the little Passport into a real PA, which will confuse the shit out of the FOH guy. Once he understands that your PA is really just a guitar amp, he'll get it. Hope that helps.-Richie