Yeah it will be fun to try crossing over the SBP higher than I'm used to and seeing how it sounds, just because it's designed to do so. We'll see if it's annoying to be able to hear the localization of the sub at the higher frequencies too. That's cool you're so familiar with the IB SBP 15's. I had to go look up who Audio Frog is, they look amazing too. They have that same type of ultra-low inductance as Acoustic Elegance subwoofers, probably because they're using a similar type of copper "faraday sleeve" around the voice coil. I'll bet they sound amazing. Those Audio Frogs look legit, and also I noticed they're all on clearance right now on their website! Dude they're selling the 10" and 12" subs for $75 right now!You can probably cross it higher, but you still have to be careful of localization. Even clean bass will become localizable after abou 120hz.
Rockyworthy, yes I've used IDQ's. I ran a pair in a sealed box, then the same pair IB. Later I added a third IDQ 10 IB. After that setup I ran a pair of SBP 15's IB. Now I'm running my first ported box with Audio Frog's base model sub the G10D4.