I have not looked much into the 2 speed pumps assuming that i have too great an amount of head loss to move enough water for it to be beneficial. I know most of the 2 speeds come in 2" discharge and since i will not be replacing all of the pipe i figured that i'd be better with an energy efficient single speed. I was running the previous pump 8 hrs. a day and had no issues with water quality, but was wanting to possibly go with a smaller pump if I could and save some $$. I'm pretty sure the pumps i looked at would be under the ~45GPM, but i was concerned with having to run the smaller pump that much more to turn over the same amount of water due to the lower flow because of head loss. I guess my question is how can i estimate which pump will put at closer to the 45 gpm optimal flow? The Hayward SP2607EE or the SP2605X7? If it were the 2607EE i was going to go with the pentair due to the greater motor efficency, price, and the flow is a little greater. The more i research the more confused i get. LOL