King Buzzo? Never heard of her
But seriously, I like the idea. Many blues guitarists use a 1x15 bass cab to get a fuller sound, or maybe they use the bass amp for a cleaner tone
And, not to rain on your parade, but have you tried an EQ? With a sealed speaker cab and an EQ, I could get the windows shaking...using a 1x12 cab. You should be able to get PLENTY of thump out of that Genz Benz ported 2x12.
Simply using the graphic eq and tone controls in the MP-2 can get mushy and overprocessed, IMO. I use the secondary EQ in my GX-700 to bump the lower end and cut the mids a bit more, so that I can leave the MP-2 more wide open and natural sounding. Sure, the MP-2 still has the bass up a bit, but it's not maxed out, same with the cut mids, they are not totally scoooped out because the other EQ is doing some of that for me.
Sometimes taking too much of a freq out of the mix (or adding too much in) tends to choke the tone a bit, makes it one dimensional, less full, less open.