Mini jet makes a power head that has an adjustable flow you can go from 40 to 106 GPH. I upgraded the stock pump to a RIO 800 in my NC 12g plus I have the 2nd power head (The mini jet) running wide open at 106GPH. I'll be honest my corals have seemed to benifit from the addition of the second pump my torch coral is puffing up more and my shrooms have expanded noticably (Spelling sorry) since I added the 2nd pump. I placed the pump half way down the left side of the tank facing the glass, if you let the direct current hit the glass it will rebound off of it to create a nice gentle breeze like flow, but it also depends on your aquascape.
Hope that helps
T$