Our Century, two-speed EcoPump needs replacing, and I've read a lot about two-speed pumps not having the power to work well with our DE filter. Several (non-seller) advisors have recommended using a variable speed pump, instead of the two-speed, saying that the slightly higher GPM makes the DE filter work better. (Going from the 1-speed to the two-speed cut our electric bill by $150/month, so I don't want to be less efficient, regarding electricity.) I would love some feedback about the variable-speed pumps working better with the DE filter. A "Speck A91" has been mentioned. Any thoughts?