Thanks again for all the useful replies, lets keep them coming in and not wind up like other threads where you have to read 50 posts to get some useful info.
the reason i am set on using ceramic rings is 1. my sump is open and visible and i like the look of the white plain colour, it also looks neater to me. and 2. i have already bought it. I might put what you guys have called some of the best bio-media i.e. pot scrubbers, at the back and below the ceramic balls as to hide them and increase filter capacity.
about 60% of my sump will be bio-media- ceramic rings, pot scrubbers and very course (not dense) sponges. all water going to the sump will be prefiltered.
What other things could i put in my sump to help it even more and make it more benefical to the tank? would some floating plants be a good idea or would these eventually clog up the sump a bit? any live critters that can go in there?? i know they cause waste but maybe there is something out there that some using and its working well.