Perhaps my careful consideration of component matching, speaker positioning and mains quality paid dividends!this is precisely the issue - anytime you have to 'carefully' match components so that the system sounds just right, you have a problem with one or more components in that chain. In this thread, it's all about speakers so let's concentrate on speakers. If a speaker is time-coherent (which B&W are not even by a long shot) then component matching becomes a non-issue. Time-coherent speakers sound good with almost any electronics & on any genre of music. Of course, the better the electronics & the better the recording, the better the output sonics.
Mark_nz
I wager that if you would have changed one item in your then-system that had the B&Ws your system would have collapsed performance-wise. That would not have been good.
Jkalman, the sibilance is a phase distortion issue & it won't go away with toe-in (like Zd542 wrote). I bet that whatever you try you will not be able to get rid of it. It's inherent in the speaker design & the 4th order x-over. The boomy bass is due to the poor port design. B&W cannot get this right & didn't get it right even in my DM604S2 nor in my friend's 803D. Port design is hard to start with - you have to start & stop a slug of air at a moment's notice given the fact that the bass from the port is 180 degrees out-of-phase with the bass cone driver. If you don't design this correctly, you get bass overhang or what you call boomy bass - the previous bass notes hung around too long & interfere with the next bass notes (from the next bit of music) & smear it.
Play some tracks from Diana Krall's Love Scenes - sibilance city if you will. Let us know at point in time you walked out of the room!
Also, like I did with my DM604S2, play some Diana Krall & careful note where the soundstage is & where DK is in the soundstage. Then, immediately next play some Frank Sinatra. Once again note where the soundstage is & where FS is in that soundstage. Any difference between the 2 soundstages?