All of the Uruguayan fish, especially the ones from the south of the country - Gymnogeophagus, Australoheros (chanchitos), and some Cichlasoma (acaras) will do well into the 50s and 60s and breed when it starts to warm in the spring.
Also, Laetecara dorsigerus (from Argentina) will do well.
For that matter, lots of central americans will do well in the upper 60s/low 70s. Saratherodon as well.