RE: power heads
i think perhaps your problem isn't so much how strong your flow is, but that it unidirectional and laminar. you need to break it up.
solutions like Hydor Flo, SCWD, Wave makers, you name it, all will do the job. remember, water movement in nature, even in lagoonal areas, is chaotic.
My first time diving I was struck by how wierd it felt to have eddies of hot and cold water moving all over my body.
personally, in a 55, I would probably do a Mag 5 w/ a SCWD on it as one of your cheapest options - and have the outlets at either end of the tank.
"Maybe in order to understand mankind, we have to look at the word itself: "Mankind". Basically, it's made up of two separate words - "mank" and "ind". What do these words mean ? It's a mystery, and that's why so is mankind." ~ Jack Handey