I have done quite a bit of research and listening on noise cancelling headphones, and can say that the Bose seem to have the best noice cancellation. however, able planet has VERY good noise cancellation, as well, and they are definitely cheaper. I can't say much about the sound quality, as i haven't done a sit-down listen session with a whole stack of these cans, yet. I would go ahead and say that the 75 dollar pair of Able Planets has nearly as good noise cancellation as the Bose.
Call me crazy, but I also thought the on ear QC3's had better noise cancellation than the QC-15's. And I went back and forth on them quite a bit.
However, I don't really like the sound of any of the ones mentioned.