Depends on what the overflow is rated at. You should base your return pump on the overflow rating not the flow you want to have in the tank. I am sure that pump will work but for a reef, you will want more water movement than that. PH's or a closed loop can take care of that though.
If you have 2 internal overflows, you should be able to handle 1200 gph through them. A typical AGA overflow will handle 600+. Not sure what you have though.