use one of the 75s for a fuge/sump for the other 75, use the bowfront for a reef tank, since the reef doesn't "need" the room. use the sump for both the bow and the other 75. Or you could connect the two 75s together
actually i'd make a list and plan how much you are willing to spend then go from there
you could always use one of the 75s for a coral propagation tank and then once a month give everbody on canreef a frag