I don't normally join in these sorts of discussions when all the good advice has already been given, but I wanted to second P mmk's post about brightness. It may be an assumption of course that the Boston's are brighter in sound than the B&W's, but if it is true, then the advice is something I have defintely experienced - - the demo sounds good, and then even after you get it home for a while, but after a time you start craving less "sheen" or even harshness and more accuracy/mellowness, which in my opinion usually means more realistic. Also, Jameswei's post is also excellent advice - watch out, you may start wanting to upgrade constantly. The only way out is to buy either the cheapest thing out there (of the decent equipment) and be content knowing it sounds pretty good for pretty cheap, or buy the best you can't afford (credit!) that you won't be able to upgrade for a long time!
That's it, as always though, have fun.
That's it, as always though, have fun.