Tiziano, why do you keep 2 different Calibres there?
Why not keep them both in sync? I use SugarSync to do just that, and it works great. Whatever I add to Calibre on computer 1, automatically appears in Calibre on computer 2 as well. (And vice versa.)
Plus, of course, it's also automatically available for download into Marvin on all my iOS devices, thanks to the SugarSync apps there.