I have spent a lot of time searching for a great closed headphone. One reason is that I use headphones in the office and don't want to bother my office neighbors at work. Also, I sometimes listen to music in bed when my partner is asleep. A good closed headphone is not at easy to find as a good open one. However, I would definitely recommend Denon or Audio Technica. They know how to make a nice sounding closed headphones that sounds "open-ish."
As for isolation, the Denon D2000 certainly isolates more than the 650s. As far as I can tell, there is little sound leakage from the can. However, they don't isolate as well as some of my other closed phones (as far as keeping out outside noise). [I can clearly hear the tv without music playing.] Out of all my closed headphones I would order them as follows (most isolating to least isolating):
HD 25-1 > Darth Beyer (or DT-770) > Ultrasone HFI 780 >> ath-a900ltd > denon d2000 > Woodied Senn 580
The first 3 phones seems to isolate me from the outside world much better than the latter three. You can get significant isolation from the first two without music playing. However, the first three are not as comfortable because of the clamping force on your head!

As far as I can tell, all of these headphones leak little to no sound (unlike the 650s).
Disclaimer: This is all from memory. It could be that the Denon's isolate as well as the ath-a900ltd's. It also depends on how large your noggin is. My trouble is that headphones are often too loose on my head. The Denons and the Audio Technica's are pretty loose. Of course, this makes them great for wearing for long periods of time.
Quote:
Originally Posted by Orcin 
I was afraid you would say this... oh well, I guess I'll just have to listen to all of them. 
Actually, one of my goals is to find a pair of closed phones that I like for those occasions when I need to block out that TV in the other room. The Denon D2000 is a prime candidate, so I also want to audition those. Do they isolate outside noise better than your HD650's?
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