Do a pair of Bolivians and skip the white clouds. You will be able to see more interesting behaviors out of the Bolivians if you get a sexed pair versus a solo one with white clouds.
yea a pair in the 15 would be ok, with a couple of catfish and you would be all set! keep the cats small, say maybe a few pygmy cats, and maybe a few otto cats, and you would be ok! snails wouldn't be bad either!