if money is no object, and even if it is, the best submerged media is gonna be bio-home, bio-home +, and bacteria house. go on arofanatics and look at their sumps. Or you can just do ceramic rings.
a lot of people recommend the seachem pond matrix for sump filtration, and regular seachem matrix for all other applications, I personally use it and have been very happy about it on all aspects... however it gets a bit expensive.