I would suggest getting rid of the bioballs, as these produce nitrates and really are not good for reef systems. In FO tanks balls have their use, but not in a reef system, and certainly not in a DSB system.
What detritivores do plan to add to the sand bed? Care must be taken here not to add predators of sandbed infauna. You'd be surprised what you think is "good" for DSB, is really detrimental. Even some fish, such as gobies, whose diet is primarily pods, is not a good choice for a true DSB natural system. Likewise, the sand sifting sea star.
Its good that you have a sump. If you can turn your sump area in to a small refuguium with macros, this will be ideal. Myself, I have a good deal of macros in my tank, but I have no predators. If you have tangs and angels, however, they will eat the macros, and demolish the macros as a filter source. In a true DSB system, your emphasis is on natural filtration rather than mechanical filtration. Your sand, rock and plant life become the filters, thus eliminating the need for mechanical filtration--except for the protein skimmer. However, the skimmer, which is "mechanical" is still along the lines of natural. Not so with things like bioballs, filter bags, media, etc.
Here are a few artilces that you might find interesting.....I'd read them carefully and take them to heart.
http://rshimek.com/reef/sediment.htm
http://www.animalnetwork.com/fish2/a...wb/default.asp
