Well I said I'd have tried the day after but much more time passed, I'm sorry ^^
Anyway, I found an easier way to solve my problem:
First i cut out all of the unique songs (this one's easy, i cut the ones i want to work on and put them somewhere safe deleting 'em from my music collection, then i do the same with the ones remaining and my music collection is empty.. and then i re-add the ones with the same hash files and they're the only songs in my music collection).
Then i could finally search for the ones that end with a number between parenthesis out of the whole and delete them.
... wasn't hard after all, sometimes we just make things harder and harder working on special features and add-on (talking about myself here, who thought about what to do exploring all of the features bundled) when the solution is much more simple.
So I installed your script and didnt need it in the end - not a problem though, It'll come in handy in the future.
Thanks again for your help.