I would start with one but in the right set up with a heavy substrate and acros one could work in a 58 or 65 tub type tank, 2 might not be too much but it depends on layout, substrate and inhabitants. The ideal would be 2 6000 and a multicontroller so you could dial in the exact flow rate you need and alternate the sides. I think my advice in this situation would be one 6060 and perhaps a Sea Swirl or SQWD system for your return to create a random flow in conjunction with the broad flow of the Stream. Remember wave makers will ruin the pump and void the warranty and their is no control possibility outside of a timer with 1hr intervals on the 6060.