Return Pump question?

I have a 68 Gallon Cadlights tank. It came with a 1" drain and a 1/2" return line. The pump that came with it is rated at 500GPH and I would obviously like to swap it our for a more powerful one. It's approximately 3' from the sump to the bottom of the overflow. In looking at the submersible pumps available, the most powerful ones are about 700GPH with a 1/2" outlet. So the question is... Do I settle for that or is there a way to work around it? I assume I could get a larger pump and work with a reducer to a 1/2" at the return line going up into the overflow. I guess I could also run a line up the back of the tank instead of using the overflow. Any other ideas or suggestions?

Thank you!