The atmosphere usually takes care of itself for the big games (apart from a lot of derbies that are a bit tense for noise sometimes).
Today should be good. Opening [home] game, opening of new tier, first big game of the season, Mourinho is a wanker, we want to win the league this year and Chelsea are champions.
It's the other games I think we might struggle. The new signing section is a great idea but I think it's going to be very small for a 55000 stadium when the rest of the ground is quiet. Might just sound like a murmur down at one end like a smaller singing section was for a 47000 capacity.
(Hopefully worsleyweb's thoughts on a proper end at the North Stand happens. That'll solve the impact problem as 12000 in one tier will make a racket!)
But that's for the future and today will be great! COYB!