beleive it or not I have never used the Grab function and don't know what it does! yes I have a vague idea it does make a copy.
I have the iTunes folder as my download folder, with iTunes integration enabled, so tunes load into iTunes automatically (usually
) I share selected folders from my iTunes folder and so never have more than 1 copy. Some advise against doing this, but it has given me no problem.
I hope that helps.