I think its a case of either or really. If you wanted some other cichlids with the Geos your best bets are things like Severums, Thread Fin Acaras and things like Blue and Yellow Acaras. Where as the Oscar and the JD would work well as tank mates so long as they had the right personality as Oscars can be quite different from specimen to specimen.
Ropefish and plec would work well - were you thinking common or an L number, I would go for an L number rather than a common as for example something like an L75 would be good, does not get too large but gets to a good size and has interesting colours and pattern. And the smaller plec means the smaller the amount of poo... I actually prefer Whiptail Catfish as they are much more active than any plec I have found and they produce much less poop... things like Lamonicthys and Sturisoma are gorgeous!
Hope that helps
Wills
