Jack:

Just get bass management that lets you set the crossover. If you want to equalize your subs - get an external equalizer. The BFD (Behringer Feedback Destroyer) gets great reviews. I have a Behringer DEQ 2496 which costs a bit more but is much easier to set and has some other features (like a great SPL meter) that I've found useful.

I wouldn't rely on SNAP or any other Auto-eq out now to actually equalize your SVS's.

BFD, DEQ 2496, Velodyne SMS-1 are all units that can be used to accurately fine tune your subs WAY better than almost any built in equalization except for some high-priced Meridan systems.