If we don't sign anyone in central defence we will be fine as we will have much better organised and motivated players and a younger goalkeeper.
I think we can afford to let Cuellar go if McLeish has plans to use Beye as a back up centre back along with Collins, Clark and Dunne. Personally, I'd like Villa to sign Dann and play him next to Clark. Clark is going to be a cracker, perhaps not ready just yet to play a whole season but he has to start somewhere.