use a laguna 1500 pump, this pump have a high turn over rate (1500 gal/hr) and is very energy efficient and quiet ... mine is running at about 60 watt
Just put a T for both returns and use one pump. This is what I am using for my 210 gal reef tank.
What else are you using for flow in the tank? As long as you have adequate flow and you are just using the return pumps for your sump return, I would say Eheim 1262 is a good choice. I have a 1260 and I love it; quiet, low heat, affordable and reliable.