actually by established many times it refers to established nitrogen cycle. discus can be placed in new tanks as long as the tank is cycled.
Marshal..look to plants that can take higher heat. swords do okay as do a few other plants.
are you looking for biotope plants or plants that tolerate higher temps?
I have anubias, java fern, amazon sword, ozelot sword,a few crypts, wisteria, water sprite and elodea(tho elodea sometimes does not fare well in higher temps) all in my discus tank..I pulled the java moss as it was a pain in the backside.