I’ll buy the headphones version of Reference 4 for sure... don’t know about the calibrated phones... almost twice the price if I buy from them, is it worth it? A bit out out of my budget atm as I’m aiming for Apollo Twin as well and Spitfire’s Christmas sale drained me as well
Sonarworks does sales on the calibrated headphones from time to time. Some are blowouts on less popular models but I got a pair of HD600s through one sale there.