i don't think there's any shops in Wales that stock a range of high-end, or or little known bass amps makes. and i live in the far left hand corner. so like you i've never had the ability to try-before-buy, and all my amp purchases have been blind*
on every occasion i've tried to build up as big a picture as possible on the properties. and to be honest, every single time the cab or amp has performed and sounded exactly as i have expected them.
i think the trick is;
ignore the 'i think (insert name) is the best around' and the like. focus on people who say things like 'i like (insert name) [i]because[/i]'
make yourself a checklist (punch, mid scoop, sparkle, clean, rich, deep etc.) and keep an eye out for when people mention these things in relation to a particular brand/model. soon enough you'll see that there are a few options that seem to tick all the boxes (as you've already noticed with the epi)
once you've got down to a handfull of choices, start searching for any direct comparisons between cabs (this shouldn't be too hard if the equipment is similar as there will bound to be a gear nut somewhere whos had both), and talk to people [i]directly[/i] who own the equipment, ie pm them asking a couple of specific question. in my experience as long as your polite and don't go on for too long, people are more than happy to talk about the equipment they own!
as long as you put time, thought and effort into it. and don't just talk to 2 people who say 'i think (insert name) are the mutts nutts' and go on that. you should be happy with the choice you come to.
*which so have have included Trace, Peavey, Sansamp, Glockenklang, Schroeder and Euphonic Audio.