Motion 20i and amp speaker settings.

[Davet70]

Now that i have my first set of tower speakers and a more versatile amp, I'm bit confused as to what setting such as size and crossover I should be running my 20i's at. I watched numerous video and read several articles on the pros and con of setting the towers at either large or small.
So I'm looking for some practical advise on what is the better(which I know is a subjective term) for setting these speakers in my amp. The amp I have is a Denon AVR-S970H.
Thanks