I completely disagree with you. The 6XX dissapointed me initially, coming from ATH-M50x I felt they lacked sub-bass impact, treble sparkle, and soundstage was not so great. But after more and more listening, I can tell you the 6XX are THE best headphones I've ever heard.
- They have an almost perfect frequency response, the "veil" in fact it's not a big deal and makes the sound much less fatiguing, enabling LOONG pleasurable listening sessions (not like the M50x, that gave me headaches after an hour or so). I said "almost" because some people might lack some sub-bass, but nothing a tube amp can't fix. And there's this warmth that's sooo engaging, making everything sound more natural... It's just a lovely sound, once you get used to it you won't like cold headphones anymore.
- Soundstage is just right, not artificially large like some AKG, not too close like most closed-back headphones.
- Clarity is just great, no other headphones in this price range will be better than the 6XX on this.
- Detail is a perfect compromise, you can spot minor mastering faults but they won't slap you in the face, so they're just right for low-quality recordings while better quality ones will be even more enjoyable.
- Comfort is TOTL, no compromises: stock pads are great, headband feels great, they're so light you literally forget you're wearing them.
- Build quality & aesthetics, for me, are just right. Nothing fancy, just headphones, they're neither rock solid nor weak, just ok. They don't look too fancy, if you're more into aesthetics maybe you dislike them, but I'd personally wear rotten potatoes on my ears if they sounded better than this.