Sump/Overflow question

[EvilTwin]

I am still trying to better understand the way that an overflow works but thought I would post my concerns and get some opinions. Since installing my sump and overflow in the past week I have been trying to adjust it for maximum effectiveness. When I first set things up it seemed like I was getting barely any flow, and that increasing the flow from the sump back to the tank was going to flood the tank. I got over my paranoia as I realized the morewater was going back to the tank the more would go into the overflow and thus increase the flow rate. Makes sense but I had never done this before. Anyway, I now seem to be at my limit as my pump, a Mag 3, is now flowing with a fill open path back to the tank. My overflow box is a Tidepool SOS, which has a single 1 inch drain, along with a second drain for a secondary overflow. The main drain is covered by a small plastic cap that contains a hollow plastic rod that, when adjusted, maintains the water level in the overflow box and prevents the gurgling sound. It seems to do a good job as long as there is enough flow. I guess my big question is, do I have too small of a pump? Should I have gone with something larger? I only have one return line plumbed into the tank, if I go up to a larger pump and re-plumb the return for two lines could I eliminate my powerheads (I have a hagen aquaclear 70 right now)? I think one of my biggest problems is I have never had enough flow and I get dead spots. I really want to solve this and I need some help doing it right. TIA.

[FragOutpost]

Before upgrading your return pump I would look into getting a high volume/low electrical consuming powerhead like a seio or a tunze. Another option is to use a mag 7 and run a closed loop if you do not want to add any more powerheads. melevsreef has a great guide for building a closed loop. More flow is almost always good as it is usually difficult to add too much.