Adding songs without duplicate in iTunes? Is there a way to add songs to iTunes and avoid make duplicates in the process ? I've a couple of macs and I want to merge all my songs on 1 mac and then be using home sharing...

Is it possible to avoid duplicating all the songs that are already in the "destination" iTunes Library ?
You should have a look at the utility "Dupin", it allows to check for bunches of duplicates and resolve the conflicts.

I would test it for a few duplicates so you see how it works, and then I would just import everything and clean afterwards.