If you can fit it, I think an 18" would be awesome just for the uniqueness factor. Any of those setups have the potential to get really loud if you do it right though, so maybe price should point the way for you?
no, the cars u listed dont have much room 2 play, u should narrow it down to 2 12s, 3 at most. but if u go wit the suv, u might be able 2 squeeze 2 15s in there. ported would be the way 2 go.