The B2 Sub is not powered, so it's not gonna do what you want to do. And, I suspect you need to work with your keyboard's EQ settings if you're not getting enough bottom end from the compacts. There are times when just using a single compact the bass is way too much and I have to make adjustments on the keyboard to reduce the amount of bass/bottom end.
I'll be more than happy to help you in any way I can to solve the problem you're experiencing,
Gary

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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)