Try using the B1 on one speaker and the SM57 on another, pretty much dead center about 1 inch from the grill, U87s work really well like this. You should find the B1 fills in the gaps from the SM57's response, so you get the bass and treble from the B1 with the nice mid punch from the SM57.
There are some great condenser mic deals, the SE mics are great too, but this looks like a real bargain!