46 Gallon Tank Overflow and Return Pump Question

Ok, I have a 46 Bow and I am building a Sump for it. I understand a good flow rate is 5x the size of the aquarium so the Eshopps 300 which has a GPH rate of 300 should be fine. That is about 6+ water changes an hour on a 46 gallon. What size return pump should i use? I want enough water in my sump, but not too much. Any advice would be wonderful. Also feel free to chime in about the correct size of overflow box. Thanks!

 

I have the same overflow on my 55g and I use a Mag 5 for my return, if that helps.

 

so you are using a 500 GPH Submersible water pump? What is the water level like in your sump?