I'm (obviously) not the OP, but I want to thank everyone for their tips. I'm a car-less bassist playing in a rock band for the first time in a long time (the last ~8 years or so has mostly been jazz, folk, and theatre for me), and my Acoustic Image Coda is very unlikely to cut it. For the moment we're just rehearsing, and there's backline in our rehearsal space, but I've been trying to figure out what I'm going to get when it comes time for gigging. I think I'm in a slightly easier situation than the OP (even without considering the sight issues) - Toronto has better public transit than Calgary, I think, and I'm not looking to play metal. The band I'm in is playing post rock, and one of our guitarists mentioned that he'll probably gig with his Blues Jr. because he figures his Hot Rod would be too loud, so I don't think I'm going to have to compete with anything too crazy.
So yeah, thanks for all the advice. This has made me feel much less worried about how I'm going to make this work.
First, WTH is post rock?

I work with a guy who has a Blues Jr. make no mistake, they cat get deafeningly loud. Nothing like a Marshall, but more than loud enough to cause your ears to ring - for a long time after the gig.
Even though I am currently using a 210 combo, I hesitate to recommend them out of hand. IME not all are created equal, some cut it and some far from it.
I'm really sick of 410's and their throw - I've had many, and every time it was double the volume 10 feet past where i was standing, causing a problem FOH, causing me to turn down and then I couldn't hear it.
I'd really like to check out a three 10, but these days the only company I know who makes one is Epifani. And I don't feel like shelling out a grand just to test the cab.
I guess that leaves 12s. I've had a GK 212 and an Avatar 112. The GK was plenty loud and reasonably compact, but had a middle of the road sound which just didn't light my fire; I thought it was light in the upper mids, with no bark. Well made, though. The Avatar was only 95dB efficient, so it took a lot of power to drive it. Deep, though, surprisingly so. I have friends who use and swear by two 112 cabs, so maybe it was me. Also, I was in a music store a couple of years ago, specifically NOT looking for a cab with 12s. The salesman - my friend - insisted that i try a GB Uber 212. It was best sound in the large store. So I dunno.
My fave cab is GK NEO 115 - III. Very barky, which i like. Not a boatload of low end, which for me makes it a good, growly cab. One thing about it - if you drive a lot of bass through it, the port becomes like an air pump which you can feel. I don't recommended that, though. But I've done an innumerable number of relative loud rock gigs with a single one of those GK Neo 115s, and liked it. Interestingly, I don't like 2 of them together.
Don't know that helps, but for me, the process of elimination leads to 12s.