Return and skimmer pump???

[Flashy2003]

I have a 57g oceanic rimless with the mega over flow and a 30 gallon sump. I think its rated for 600 gph but not sure. I am currently running a mag 5 on my Aqua C Ev 120 Skimmer and a Mag 7 for a return. The skimmer needs a bigger pump so I was going to put the 7 on that and get a 9.5 for the return. Will the 9.5 be to much? IF i turn it down will it burn the pump out. Thanks