Upgrade - Front End OR Back ???

I have a dilemma. Currently I have an Esoteric X03SE, Luxman P1-u, and Audeze LCD2 headphone setup and want to upgrade. What will be the "bang for the buck" upgrading to an Esoteric D03/P03 or upgrade the headphone side (Woo WES with Stax SR-009)?
Thanks in advance
I feel your gear it top notch at this point - "bang for the buck" gains will be vibration isolation, power conditioning and cables unless you are already "arrived" with those.

I don't know what you're running right now but I can recommend from my experience. On the vibration side I'd recommend a SRA VR3 for the headphone amp and on the PLC side RSA Haley would be quite and upgrade. What cables are you running with?