I find the DT770 to be more comfortable than the other headphones you listed. I wouldn't call the other phones uncomfortable, but for me, they can't touch the DT770 in comfort. I owned the QC15 for awhile (gift from my med school to compensate for loud construction). My experience was similar to yours. They are comfortable and the isolation is good, but the sound quality is not where it should be for that price point. What I found truly shocking however, was the DT770's passive isolation is very close to matching the QC's. Not only is the isolation great, but there is very little leakage as well which your roommate will appreciate. I'm not much of an active noise cancelling guy so I haven't tried the UE6000. I avoid blanket statements but i feel this one is true: active noise cancelling causes sound quality to suffer. I always chose good passive isolation over good active noise cancelling.
The 840's might be a good fit for you. In fact, you might like them better than the DT770's. I'd say you really need to try those two out to see which you like better. I like both, but prefer the DT770's overall because they are simply more fun to listen too. The 840's are more analytical but still have an overall warm sound sig. I think you would be very happy with either of these phones. Give them a try if you can.
I have very little experience with the BW's but have listened to them once. Unfortunatley for the BW's, I listened to the ESW9's right after to compare. I found the BW's slightly more comfortable but the ESW9's blew them away in terms of sound quality. Full, warm, tight. Man they sound great.