I don't see the need to add powerheads. You are getting good movement with the Fluvals.The power heads wont give you that"lift" you are getting from the airstones. The water is drawn upwards by the air bubbles. You would probabaly save a few bucks on electricity if you kept the airpump. How many powerheads were you wanting to add.
Powerheads are better, and if you want lift, do what I did. Add a lift tube from a UGF filter to the intake to the powerhead and draw water from the bottom of the tank to the top. If you want more, PM me and I will take some pictures of my setup.
