I don't think it would have been prudent for the Packers to have signed Julius Peppers and Jarius Byrd in the same off season considering how much each are due to make, and the guys we have coming up for a new contract.
With that being said through an admittedly small enough sample size it appears Thompson made the right decision in passing on Byrds 6 year $56 million dollar contract in favor of going with the current safety group & drafting Dix as well as signing Peppers to a 3 year $26 million dollar contract. It's basically opportunity cost. Peppers plugged a big hole as a consistent playmaker opposite Matthews, and Dix has stepped in well and made plays as the new guy in the safety group and made much less money than Byrd.
I'm interested to see how Byrd bounces back next year though.