i have both SD MP2 and SD 722 and i wouldn't have thought to run the mp2 in front of the 722. but that is also because i wouldnt probably want to run the 460's transformers into the mp2's transformers... might be a little too much snuggly warmth for my taste.
i really like the mp2 with the AT853 and the VP88... gives both of those mics a bit more something to bite into. but i probably still wouldnt run those mics into the 722 since i typically use those mics for low pro stuff.
the earthworks might be fun in front of the mp2 > 722, but straight into the 722 would probably be adequate to say the least.
imho, a box would have to be very well paired with or complement and balance the mics or just super awesome to warrant me thinking i would need something else to tote around. more shit to turn on, power, cable up, go wrong... i went to the SD7xx for a bombproof all in one.