Any bacteria based bio filter is going to reduce the nitrogen compounds to nitrates. A drip water change system is a great way to rid your tank of the nitrates.
The part of my trickle filter I am most impressed with is the water oxygenation. My 110gal is way over filtered but I added a trickle filter because I picked it up for only $30. I saw no change in water tests (Nitrogen products read almost zero before the trickle filter addition). Man did I notice an increase in my Cichlids activity though. They were always active but now they seem much more so. I credit this to better water oxygenation... weather I am correct or not is another topic.
I can't see how having too big of a sump would hurt anything!