Well, since you've got an H/K, you can do that. I doubt that there is too much sub 100 Hz stuff going to the surrounds in any case. (or at least, not enough to localize to the sub) But I'm just making stuff up, here. Personally, (even though I've only had them 3 days), I'm crossing my M50s at 60 Hz.

I am the Doctor, and THIS... is my SPOON!