you dont need that much flow through your sump- 3x to 5x, thats it. Lets do the math problem:
55 x 3 = 165gph
55 x 5 = 275gph
Now that your know the range your looking for, lets look at the pump statistics. Ok, these number are after 4 feet of head which is about normal, unless you have a basement or remote sump.
Mag 5- 310gph
Mag 7- 450gph
mag 9- 800gph
You are already over with the other two and the Mag 9 is like 4 times what you need, the Mag 5 or 7 cranked back a bit with a T back into your sump should work fine.
HTH, Mike