At least you have more room to play with Pumps. I was looking at the Hydor Pico Centrifugal Pumps. They have one rated at 300gph but it wont fit in the 2 1/4 x 2 1/4 space I have to work with on my JBJ AIO. Want to get rid of that "under-performing" 76gph one that it comes with.
I almost bought the JBJ AIO too. This should fit your JBJ AIO:
http://shop.mediabaskets.com/Aqueon-QuietFlow-Submersible-Utility-Pump-600-ES06616.htm