Barreto could be excellent for Juve... but my worry is this. He could easily end up a player like Almiron, completely unsuited to Juve.
I think if Xabi Alonso isn't an option, they should look Italian... Aquilani, Montolivo and Cigarini. Not to say that they should only look at Italian players... just that these three candidates fit what Juventus needs.
Cigarini is the weakest of the three, but likely by far the easiest to obtain. He's also proven he can work in a Ranieri 4-4-2 and could probably work well with Sissoko.