Well, as you mentioned, B&Ws are quite popular.
Personally, I use:
NHT 2.5i main monitors
REL Storm III subwoofer
MIT Interconnects and combination of MIT and Kimber speaker cables (I firmly believe cables make a pretty big difference...)
The great news (IMO) is that the NHT's are now incredibly cheap. I've seen them go for <$500 on ebay!!! They are still amazingly awesome speakers (absolutely ruthless though...seriously. If you have crappy cables or amplification, you'll know it. If your CD sucks, you'll know it...)
Also, Rotel amps are damned cheap considering what you get. Plus they sound friggin amazing. IMO, you'd have to pay considerably more to get anything that sounds even marginally better.
As for other varieties of good mastering speakers -
-Vienna Acoustics Beethovens
-Vienna Acoustics Mahlers (I would gleefully remove my left nut with a pair of kitchen sheers if someone would give me a pair of these!!!)
-NHT (whatever their new lines are called now)
-Wilson Watt/Puppy (WAAAAYYYY overpriced though!!)
-Paradigm (their entire 'Monitor' series is quite nice and damned affordable - thank you Canada for some damned fine gear at good prices!!)
-PSB (see Canada remark above...I'm not AS big a fan of these as I am of the Paradigms, but their higher end line is quite remarkable for the $$$)
The thing that ALL of the above monitors have in common is that they are all full range (with the exception of the smaller Paradigms - but they're damned close) and they are all dreadfully accurate (read:not euphoric) loudspeakers.
All of these will demand only the finest sources whether it be components, cables or music. If there is a flaw, you will notice it.
Also, I really prefer using a subwoofer while mastering. My personal preference is the REL line - I have yet to find a more accurate sub which does JUST that - only sub-bass. My Storm III kicks in for less than an octave, but damn is it worth it... Of course, the ST line is dreadfully expensive. Their entry-level stuff is still quite nice.
Also Sunfire, Velodyne, SV, and a few others do make good sub-bass systems.
Good luck on your quest. Unfortunately it may be the quest for the holy grail. Fortunately, however, you will not likely need to launch any crusades nor should you encounter any Knights Who Say "Ni".