Getting rid of bio-balls?

I plan to use a prefilter such as a filter sock before the water flows into the bio media. I've heard shotgun shell wads work as good bio media, I might order up a bunch of those.

I drew up a diagram of what I had in mind for my plumbing setup. Any input would be appreciated. My display tank is 77gals. I think the layout of this sump is perfect for bio balls, thought I guess live rock could go in that chamber just as easily. This is a new setup and as far as my understanding goes I think it's better to start up a tank with bio-balls, and IF they start causing too much nitrates then you can think about removing some of them, but I think with a prefilter and a maintenance schedule there shouldn't be any problems. And I think a bunch of bio media is a lot cheaper than a bunch of live rock.