I have not visited Armoor, but can tell one thing, all Navnaths didn't lived at any place as a team. You can also confirm this point from Navnath Charitra. Many places in Maharashtra and Gujarat have stories linked with Navnaths, may be this is another one. What I feel is, some great Yogi of Nath sampradaya might have lived there, and because of his great devotion towards Adi naths the name "Navanatha puram" came.Regarding Adbang nath and Cherang nath :
It's very common in devotees to replace Revan nath for Cherang nath and Kanifa for Adbang nath.
See these prayers :
matsyeendra gooraksha jaalandharaadyaa gahanii kaaniifaa cheeranginaathaah /
bhartari charpaTa naaganaathaah bhuumyaambabhuuvuh navanaatha siddhaah //
matsyeendra gooraksha jaalandharaadyaa gahanii aDbanga chouranga mukhyaah /
bhartari charpaTa naaganaatha siddhaah bhuumyaambabhuuvuh navanaatha mukhyaah //
Revan nath is often included in the list of Navnaths but it's not sure that he is one of the first nine. Again he is called as Revana siddha, which is another name of Revanacharya, a great Veera Shaiva
Cheranga nath/ Chauranga nath is one of the Navnaths. He lost his hands and legs by punishment, being wrongly judged by hs father, and got Mantropadesha from Gorakh nath. and, Adbanga nath is another desciple of Gorakh nath. Being pleased by his innocence, Gorakh nath gave him Drigdeeksha and asked him to stop all thoughts as they arise. Adbhanga nath did great Tapasya and became one in Navnaths.