Dalis are lovely things, with the correct positioning (as has been discussed a few times on here they are actually designed to be fired straight down the room rather than toed-in due to their dispersion characteristics). Not trying to put you off auditioning them, far from it, but I would say that you should probably have a think about what you would like to hear when you try them out, i.e. what improvements you might want over your current setup. Also as we all know, room acoustics play a big part in the ultimate sound you hear, so given that you are not so easily able to get out there, it sounds like the perfect reason to find a helpful dealer who can bring them to you at home to try out.
Of course if you are happy to chop & change for the sake of it, then there's no problem at all
and that's a perfectly valid thing to do if it's what you want ("scratching an itch"? I've just done the same myself, although it's not gone well....)
I think there's folks on here that run two subs but also those that are quite happy with one. The main advantage I can think of with two, and I'm not speaking from experience here, just logic, is that if you have a difficult room acoustically then you can place the two subs and dial them in with appropriate settings to minimise room interactions and get an even frequency response, but I think it can be tricky to get the integration right between them both AND the main speakers. I'd probably say that REW should be your best friend with this (as well as a "trusted" pair of ears in the shape of a local friend who can assist)
