I don't know of a good primer for bass management. The ICBM manual might be pretty informative, as I recall it had some good information on how to determining crossover points as part of the setup documentation on it.

Quick description of what the concept of crossover is: many speakers (particularly bookshelf speakers, but also most towers as well) can not reproduce sound all the way down to 20Hz (which is basically the lower limit of human hearing). Instead, we rely on the subwoofer to handle everything from 20Hz on up to somewhere around 60Hz to 120Hz (or higher). In Dolby Digital and DTS (and to a certain degree Dolby Pro Logic before them, but we'll ignore DPL for the moment), there is a separate channel of sound that is purely low frequency, but the other channels are still "full range" -- meaning they include sounds as low as 20Hz, and that information will by default go to your main speakers. If they can't reproduce sounds that low, the sounds will be lost and there will likely also be some distortion or undesirable noise from the speakers attempting to go beyond their range. In order to avoid that loss and noise, we'd want to use the subwoofer to take care of the low frequency sound (and since very low frequency sound is largely omnidirectional, it works out OK to gather the low freq. from all of the speakers and send it through one point). That's where the crossover comes in -- it strips away the sound below a certain frequency from the speakers and re-directs it to the sub. The problem is that we all use different speakers, and the lower limits of those speakers vary -- so you can't just say "we will take everything below 60Hz and send it to the sub" since some people might still lose some sound (such as if their speakers couldn't handle below 80Hz, or if they want to make more use of a sub that sounds best if it handles everything below 100Hz, for example). So you have to make the crossover control be variable. And since most of us use different speakers for mains, center, and surrounds, it would be nice to be able to assign different crossover points for each group (it's worth noting that this capability is currently extremely rare, but will be included on the 950). For example, my mains are rated to be able to get to 40Hz pretty reasonably, but my center really can't go much below 50Hz and my surrounds probably not below 60Hz or so (maybe higher). More extreme variation is fairly common.

That didn't end up being a very quick description, but it should give you an idea of what all the crossover fuss is about. Anyway, you can also take a look at the ICBM manual (start around page 10 -- the manual is available on Outlaw's site) for more on the subject. Hopefully the 950's manual will provide some sort of advise on bass management, too, since they are including several different bass management schemes. Your current receiver may allow you to set a single crossover point for all of your speakers, but it is also possible that it doesn't give you any capability for bass management, either.