Many tube amps do not work well with B&W's (and a lot of other speakers) because of their impedence, both nominal and min/maximum, not because of their efficiency (so much). Optimally, tube amps like to see flat impedence curves about 8 ohms or higher. Speakers with dips below 4 ohms can be a problem and speakers with big swings in the curve as well can be a problem.
Speaker efficiency is not as important except as to volume potential. Actually 18w will give you some moderate sound levels in a modest sized room BUT you might no like the sound at all.
Your new amp will probably have 4ohm out put taps. Hock up to this, don't overdrive your speakers, and you'll damage nothing. BTW, be very careful in your selection of new speakers. Many folks advertise how their speakers are tube friendly when in fact they may not be at all.
Hope it all works out for you, you've taken a difficult approach to getting a good system(to your ears) by buying a small SET amp without having specific speakers to match it with. :-( IMHO of course.
Speaker efficiency is not as important except as to volume potential. Actually 18w will give you some moderate sound levels in a modest sized room BUT you might no like the sound at all.
Your new amp will probably have 4ohm out put taps. Hock up to this, don't overdrive your speakers, and you'll damage nothing. BTW, be very careful in your selection of new speakers. Many folks advertise how their speakers are tube friendly when in fact they may not be at all.
Hope it all works out for you, you've taken a difficult approach to getting a good system(to your ears) by buying a small SET amp without having specific speakers to match it with. :-( IMHO of course.