I know I should listen to it before I form impressions, but I've read a lot about the HD800 and it's almost unanimous the agreement that it's a pretty aggressive headphone. I'd love to hear em someday, possibly beside its 'S' companion before I decide whether or not I want it. Other than a few nitpicky views, everything else about the HD800 seems positive, and that's very appealing. But I still have to judge whether or not I actually 'need' another headphone after I get the HD650. Sure, I'd LIKE something closed back, and maybe a CIEM someday, but after the HE-500, it's really all down to taste now. I'm hoping that I can afford the luxury of having a slew of impressive cans to enjoy my music with, but anything above $650 is going to have to pass a lot of tests in order for me to justify spending it. That, and I really don't want to spend any more money on a single component than what the Gumby will cost. And now I'm blabbing, so I'll go back to the 800S.
I think this can will be a good deal for Sennheiser regardless of its price because it offers the luxury of personal choice in listening taste. If it takes everything the HD800 is good at like imaging, soundstage, clarity, and tones down its more aggressive nature to make it a more relaxing can, then anyone can have one of the best headphones ever made in one (or both!) of the 800 model leanings. I like the idea.