Question about upgrading circlet type headgear

[Schuey]

Ok, I have gambled some interesting circlet type helms. I want to upgrade them. Which of the items types are "normal" "exceptional" and "elite"? There are 4 types, so I am confused. I have not tried to do this yet, but I plan to soon, so any information will be helpful.

Dave

[Ruvanal]

Circlet -> Tiara -> Diadem

Coronet -> Tiara -> Diadem

[Schuey]

Thanks alot.