Sorry I didn't chime in sooner, but didn't think you were going on an electronics buying spree so soon. I would have recommended choosing the speakers first, then choose an amp that has the appropriate power and sonic traits that match well with the speakers and your sonic preferences. And same for the latter with the preamp, which IME and in my system has a greater impact on sound than the amp although YMMV.
B&W speakers are fine, but there are lots of excellent speaker manufacturers out there so not sure why you're focusing only on B&W? If you haven't yet had the opportunity to listen to some other speakers I'd make that priority one. Getting that perspective is critical IMHO to be able to choose speakers that are truly a good fit for you. Other than imaging and soundstaging I don't recall seeing what sonic characteristics are most important to you so can't really make any other good recommendations at this point. I will say that if imaging/soundstage are important, brands such as Joseph Audio, Vandersteen, Reference 3A, and Silverline (just to name a few off the top of my head) are some speakers you should try to hear. Anyway, just my 2 cents for whatever it's worth, and best of luck in your search.
