Alright, I've checked both. First, Livy and Polybius hardly mention anything about the Kaikos battle but the terrible, ferocious nature of the Galatians and that even the Seleucids feared them, and that the kind and bright big daddy Attalos defeated them at the Kaikos springs, near Pergamon and in Caria. No word on the troops he used, though, and this is the only bigger battle where Pergamon fought on its own. At the battle of Magnesia, they mention ''Pergamene cavalry'' and hoplites/phalangites.
And RTR VII gives Epiros the normal Hippeis. As I said they should maybe get stronger hippeis than the common Greeks. Also, RTR VII has Paionian cavalry for Macedon and Epiros. I would support adding them to the Macedonian roster, not so for the Epirotes, though.