If you haven't seen it, Drop is doing a run of a modified Sennheiser HD820 for a nice price. It's $1100 with $200 worth of Drop Points for a future purchase. I've stuck with the HD650 and the Drop HD 6XX for use with my Crack, but this has gotten me to finally move up to an 800 level. The Drop HD6XX was a good deal and an interesting variation on the existing Sennheiser headphones. Big drawback is that this is like a kickstarter deal where delivery isn't until November.
https://drop.com/buy/drop-sennheiser-hd-8xx-headphones?utm_source=Iterable&utm_medium=email&utm_campaign=2016123&referer=U6373M&mode=guest_open&iterableCampaignId=2016123&iterableTemplateId=2767466
https://drop.com/buy/drop-sennheiser-hd-8xx-headphones?utm_source=Iterable&utm_medium=email&utm_campaign=2016123&referer=U6373M&mode=guest_open&iterableCampaignId=2016123&iterableTemplateId=2767466