I think as far as details, soundstage, bass and treble go, W5000 is pretty close, at least out of my two setups.
Definitely closer than others mentioned.
Midrange is humped so they are not as neutral as HD800 but if I was looking for closed alternative that would be my first choice.
Had Mad Dogs, LCD-2.2 (not LCD-XC), D5K and now TH600. None of them even close to Senns sig and resolution.
The HD800 is not closed tho lol.
I think if you are getting a fancy pants pair of closed, you might as well get one that takes advantage of being closed and does it well (aka has great bass)... ala what I've read about the TH900. (rather than try to find a closed that is trying to be open with super neutral/great sound stage)