Hmmm...the aba aba would easily outgrow a 180g tank. I believe an e-eel would to. I would try large Wolf Fish or since some SH species are legal where you are at, def. check into that. As far as Cichlids...Dovii or Umbee...
I'd go for a Jardini. There's one at the LFS I've been eyeing for awhile. . . . used to be 3, and I'm not sure the other 2 were sold, so I've got a feeling the one that's left is a real bruiser.
First I'd take the tank and drown fools that thought all arowana were of the same species. (They're of the same family, not species.) Afterwards, I'd probably feed the body to a lungfish that will reside in the tank.