Okore.
For 2 reasons.
1. He appears to be the highest rated of who we've bought. Doesn't necessarily mean anything, but it enhances the hype a bit.
2. IF he does turn out to be as good as we think he might, he could help to transform the team. I think we'd all agree that a better defence last season could have given us a very very different season. If Okore urns out to be the business, he could be a hug epart in really sorting the defence, which would do wonders for us.