Ok yeah that certainly would create a bioload! Like I said, since you have a sump you may as well use the space, can't really have too much if it's in the budget. I've seen pics of sumps that are full wall to wall of bio media. The worst thing that can happen with too much media is that some of it won't be colonized by beneficial bacteria, but you'll have the extra surface area needed for more BB if your bioload ever did increase.