The media that's included from the factory is actually pretty hard to beat IMO. If you want more bio, you could run the factory setup in one filter and on the other cut the foam block in half and add two more bags of Biomax. You need to have some of the foam still in place in order to keep nasty stuff from getting into your bio.
I have ac's on all my tanks and pond too, on a brand new tank using tap water I use sponge,bio balls and charcoal, after 3 days I take out the charcoal.