Quadruple crossover is a good thing, I think! The Outlaw 990's sibling, the Sherwood P-965, didn't even have dual crossovers, which is one reason I wouldn't consider it, since I use the 950's triple crossover.

As to your question about if quadruple crossovers would be needed if you've got full range speakers all around, my understanding is you wouldn't need any crossover, whatsoever. That's assuming of course that you really do use them as full range all around. It's great if you can do that. In fact, that's the best of all worlds, I think. Unfortunately, I can't do that in my setup. For one, I can't position my surround speakers far enough from my walls to be able to use them as full range. Two, I can't afford full range (which to me is +/- 3 dB at 20 Hz) speakers times 7. Times 2 is my limit, financially speaking. So for me, I like the crossover. Even if it's only used as an option, some of the time, it's better to have that option, I think, than not have it available.