Hi Ausbloke
As for your filter, I really wouldnt think about cleaning it yet, as the tank is fairly new in running time. Since you are still adding new fish to your tank I would leave it as it is, since there is a lot of beneficial bacteria growing in your filter media.
I think that IMO if you decide to add those four gouramis and 5 more neons you will be just about stocked without going over. If you decide on a bottom feeder you may want to omit a pair of those gouramis. I would keep the idea of the dwarf gouramis and omit the pearls.
