all propellor power heads have to have a stop mechanism on them if they start spinning the wrong way, in an impellor pump, it doesnt matter, propeller it does.
so when they start, as darg said, they rattle, they are banging the prop against the stopper till they randomly spin the right way. long term, you'll destroy it.
6055 can use their controller.
makes you feel any better, you wont likely get any tunze powerhead for atleast 1-2 months.