I've used CK with Biotera Gel, Deva UDG, and CJ Curl Queen, all with very good results. With Biotera and UDG, I've tried both mixing and layering (both worked well). I haven't had the Curl Queen long enough to try mixing it with CK, but that will be one of my next experiments.

3a/f/iii
Modified CG since 11/5/11
CLEANSE: VO5 Vanilla Mint Tea Clarifying, DevaCare No-Poo, CHS Treatment Shampoo
RO: DevaCare One Condition, SS Caitlin's Conditioner, Mop Top Daily Conditioner
LI: SS Repairing Protein Treatment, CHS Silk Leave-In
STYLE: Re:Coil, Curl Keeper, Deva Ultra Defining Gel, Curls Rock Amplifier and Strong Hold Mousse, Sweet Curls Elixirs Okra Gel and Hard Hold Gel, SS Curl Enhancing Jelly and Firm Hold Gel