You might try playing with various setups in the http://ebikes.ca/simulator
and see what combination of things performs most like the way you want.
I can say that the MXUS needs some amps to wake it up; I'm using one in a 20" (16" moped tire) wheel on the left side of SB Cruiser, with a 14s EIG NMC pack but only a 30-ish amp controller, and while it will get me going by itself, and it will even haul me up a small non-steep hill by itself, it takes quite a while of max power to get me to 20MPH cruising speed, and I only get to about 10MPH before topping the hill, maybe 1/8 mile from the bottom of it.
When I add in the X5304 in the right side wheel (basically same controller running it), I get there right quick, but by itself it's about the same as the MXUS.
If I had say, an 80A or maybe 120A+ controller on each motor (or even just the MXUS), I'm sure it'd be a whole different ride.