I wouldn't be so sure we still need to sign a center at this point . . . unless there are more dominoes to fall, having KG / West / Bass / Wilcox is way too many guys for just the power forward rotation. One or all of those guys will play significant minutes at center, and one of them will probably start. There's also JJJ, assuming he isn't part of the trade.
Also, we'll need to fill a roster spot with a capable wing backup (jason richardson or rip is my guess) if green is part of the west trade.