Flow for 6 foot tank

I have a 6 foot, 150 gallon tank and looking for recommendations to replace some power heads. I have an MP40 on each end of the tank and I had also been using 2 Hydor SmartWave controllers that each control 2 Koralia powerheads. This seemed to work quite well early on, but since the move and setting my tank back up the Hydor does not seem reliable. There are times when it switches from one pump to the other that the powerhead is running in reverse and sucking water instead. I have done some reading and this seems like a common problem.

I am looking for something economical to supplement with the MP40s, and my corner return from my sump. What are recommendations?

 

What is your placement, 4 on the back glass?