what other filters will fit the FLUVAL EDGE 6.6?

Long story short, I do NOT like the fluval edge / AQUACLEAR/HAGEN made filter. I've had the filter since JUNE 2012 and since then, I have had to repeatidly clean the impeller, always needs to be re-primed as it often loses suction, makes noise, etc

I want to change to a non Hagen/Aquaclear filter for this reason.

I need a filter that SELF PRIMES ( without me filling the chamber with water if it loses suction or when I do a water change ) and something that "FITS"
The opening doesn't accomodate much ( 5 inces across by 4.5 inches deep.

Anyone else have to swap filter and what did you get? SUGGESTIONS please!!!

Thanks!