Esther definitely works over Sofia, and I agree with most that Christina is just a bit too much for Esther to handle, especially in a gauntlet-style situation like many have suggested.
That being said, I LOVE the prospect of Kat taking on Esther. Kay's been getting a lot of attention lately, and the idea of her coming into the exchange cocky then being "shown how it's really done" by Baxter is great. Maybe Kat even plays dirty a bit, going for some scratching and clawing not typical to a traditional titfight. To teach her a lesson after she's defeated, Kat's pale face is engulfed by Esther's ebony tits for a smother to knock Dennings down a few pegs.