Rich,
It really depends on inhabitants and how you use the pumps, I would use tide mode in both of you guys tanks and so only one would be on at a time. At IMAC I used two 6000's with the new 7095 program "Interval II" which keeps one pumpo at 30% power while the other pulses, this was on a 75 and it was no problem. Remember the ocean can kill you so the flow in our tanks is normally no where near a proximation of the ocean, even on a calm reef the flow is greater than we normally provide. The magnet holder would be a good choice but certainly it could be done with the standard hardware.
The Magnet holders should be out by the end of July.