i currently have a sea swirl, closed loop sqwd, and a loop operated by mag 7's...and another loop on a mag 3... i am wondering what if any difference it would be to use a 6100(i believe this is the controllable unit) in this arrangement...should i just dump the other loops and use the swirl(main return) and the 6100 on opposite ends? 2'x2'x6' 180g acrylic...am i correct in thinking that the non controlled units are heavy duty powerheads? since the controllable "powerhead" is a surge device, no? thanks