Ummm, I have 8,000 gph on my wife's 150 gal.
Two 3600 gph darts on closed loops, 1000 gph return from the sump.
I'd say in a 55 gal you could easily have a 1000 gph seio on each side, plus a return line. For me, you have great flow, but definately not too much.
Adam