Regardless of the tonal nature of the speaker, the auto setup/ EQ system will try and get the best out of them, and EQ them so they're tonally neutral. Obviously some system are better at this than others, but the point is it doesn't matter of a speaker is too bassy, as there are plenty of things you can do to reduce bass. Ideally, CM1 would be set to small anyway, as would the centre speaker - it'd be up to you if you set the CM8s to small as well.
The first thing I would so is use the outer part of the two part bung that B&W provide with their speakers.