I really like Heinze as an individual player. But defense is more than a collection of good defenders. You really really need a leader in that pack who can organize, and call out his teammates when necessary. Even playing at a local level you feel the need of that charismatic personality at the back. And I am sure pro-players would recognize that more than us mere mortals. There is a reason why they also talk about that commanding CB in every team, and I am not sure Heinze has the personality to become "The Man" in our defence. Chiellini might make it in the future, but as it is he is quite young and needs experience, and we surely can't expect such commanding performances from the likes of mistake Boumsong, and Legro. We need a real quality ture CB - and DD probably knows that too.
From players we have been linked with I like Milito and Lucio most. I thought hard about it, but I think those two makes most sense. They might be on the block in Calcio Mercato, and both of them might look to step a club or move to better leauge to prove themselves. Most importantly, they possess fantastic ability with vast experience, and leads their respective defence, and at the same time reaching prime age of their career - meaning they are also excellent financial investment. Concentrate on those two, I say, and have Barzagli as a back-up plan.