Already sounds like you're overstocked to me...for a 6 line anything under 30G is pushing it. 1 clown ok, but two seems like a lot...
So I wouldn't recommend adding anything else, no. Especially since clowns can get ornery with new inhabitants: royal grammas are peaceful fish and they'll likely beat the tar out of it.
firefish, ocellaris clown fish
caulastrea, green star polyps, palythoa, zoas