As much as I am a fan of Ribéry's talent - I started the original thread 18 months ago - I cannot see us having the financial clout to even think of us negotiating with Bayern Munchen. We should have signed him two years ago in the winter break when we were in Serie B to start the 2007/2008 season in September 2007.
The sort of fee that he would command freezes us well out. He will probably stay at Bayern or, eventually, switch to Real Madrid.
So, if it was a choice between Diego or Silva, it would have to be Diego. Silva is most unlikely ever to play in Serie A. Only Benitez would stand much of a chance of prising him away from Spain.