So I recently set up a 40B and I made my own filter for it using this method except I only have 2 pipes running down the side and one powerhead.
River-Tank Manifold Design — Loaches Online
I'm using this powerhead
Penguin Aquarium Powerhead for Fish Tank Aeration
145gph was the least my LFS carried and I figured would be good for the tank since it will cycle the water a little more than 3x per hour.
Now the problem I'm having is all my floating plants get pushed around a lot and get stuck on one side of the tank. No matter where I put them or how I angle them they end up back in the same spot. The plants are Water Sprite, Hornwort, and Pennywort. Hornwort is the only big one right now as the other two were planted when I bought them so they're adjusting to the floating lifestyle. If there's a way to baffle the powerhead some so it doesn't push the plants around so much that'd be great. If I have to though I will go and buy a weaker powerhead as long as everyone thinks it will still filter the tank enough.