Charlie and the fish tank factory used to be the best source for ceramic rings.
What media is "best" is highly debatable. Since everyone seems to agree to disagree about it I found it easiest to just incorporate several means of bio.
I'd use ceramic rings in the 1st and last chamber and pot scrubbies in the center in a wert/dry configuration fed off a "T" in the return line so some of the water that would be returned to the tank flows through the wet/dry.
Best of both worlds. This is exactly how I set up my last sump and I'm pretty happy with it, except I just built the wet/dry part out of a 20 gallon tank and set it on top of the sump.
What ever happened to him? I still need about 509lbs of ceramic media. LOL He disappeared about the time I was ready to order.