Return pump as a source of flow?
 

i have a approximately 22 g tank with a 15 g sump hooked up to it and i was wondering if i could do away with power heads, and instead, use a more powerful return pump to provide the necessary flow for my aquarium.

im considering using a mag 9.5. would this suffice if i split the return into two separate lines?

Yes you could easily avoid using powerheads in that tank with a larger return pump. The Mag 9.5 will be more than enough, I would consider smaller, even the Mag 5 will be plenty.

Just be sure to watch for dead spots where waste will accumulate. You lose some of the flexibility of powerheads when your return lines are your only source of flow unless you are using a flow director which I highly doubt on a tank this size. Installing ball valves on each return line (assuming you are using more than one) allows more control of the flow on each side. A SWCD is another option for this setup, it will give you an alternating flow pattern.