Filtering a fish only setup?

[ja5per_uk]

Now that my nano cube is up and running, I am contemplating setting up a Fish only setup for the likes of an emperor angel, clown or black trigger, tang and a wrasse.
I'm aiming for a setup that would be a 5x2x2 or 4x2x2 (with sump), my question is can anyone tell me the best filtration for such a setup. I will be using a skimmer just unsure on the biggest one to go for yet.

Any advice would be appreciated

Thanks Jason