That certainly is a good idea. The sumps allow you a great deal of versatility in regards to extra forms of filtration. I used to have a UV filter in my sump: the Green Machine. I liked that it created a bit more turbulence, plus the UV sterilization is a bonus. I currently have a powerhead with an air line connected to stir up the water and keep it well oxygenated.
When I get some extra cash, I plan on putting a media tumbler in one of my larger sumps, just not sure which media I'm going to go with. Torn between a good bio media like K1, or possibly something like Purigen.