I cannot say that the HD6XX sounds boring at all. I find it intimate and compelling although I prefer Sundara because of the sounds which seem to come from way outside my head.

"hope that these last at least a decade" - in that respect you may have been better off buying the Sennys - I'd happily launch them across the room and expect them to work fine. I cannot say the same for my beloved Sundaras. Just take good care of them, avoid dropping/throwing/ abuse.

​

Edit to add : that is a mighty fine 1st set-up, you have good reason to be proud of it. Thinkpad posse represent.