i want to sell my aria but...

hi after 19 years owning my present electro acoustic ive decided to trade it up and get myself a nice martin. i have been very happy with this and at one time played it daily for hours on end. it still sounds great.

it is an aria elecord in sunburst red. cutaway.

The problem is i have no idea what it is worth, i paid about 400 quid for it 20 years ago, and it was used then. i cant find a review for it nor similar model on sale anywhere.

anyone know where i can get help or a good guitar marketplace i can search for similar?

Harmony Central has a review section where people often mention what they paid, don't know if yours is listed or not. Or you might try asking in their forums. They have a for sale section as well.