I find Senderos vastly overrated - clumsy, slow - a trait I saw in Daniele Bonera. If you were talking about Kolo Toure then I will change my mind. But I am almost certain that better young defenders than Senderos will emerge overtime and there is no reason to commit to what I consider as just above mediocre quality player for an exorbiant fee. I mean how foolish you have looked had one bought Bonera for the price that was quoted 3-4 years ago? Was he better player than he is now? I don't think so. Young players are essentially valued based on the future extrapolation of growth, and my gut instinct suggests Senderos isnt anything special.
I agree with Mark77 on strategy we should pursue. I like Barzagli but if that kid in Genoa has potential to contribute then we should keep him for next 4-5 years and check his development. Young famous defenders, IMO, mean jack sh*t, because the age they mature is around mid 20s. Look at John Terry, for example. If one told me the John Terry that got owned by Massimo Maccarone will somehow turnout to be a worldclass CB - I would have laughed my ass off. Hence I find the policy of spending millions on young CB before the age of 26 to be rather stupid unless the defender is named Canna, Nesta, or Mexes. Senderos aint no Nesta, Canna, or even Mexes.
I like Eboue a lot more. But the jury is still out as he hasnt even competed at the highest level for a year yet. Even Legro had one phenonmenal season.

. But I like his chances of becoming a quality player.