by sound isolation Ty meant to ask - if you care if people near will hear your music or do you want block sounds from outside.
I like Open back headphones, which while don't do much at all for sound isolation in or out, they tend to provide best long term comfort and open soundstage.
From headphones I own AKG K712Pro are most comfortable and Senhessier HD558 are close in sound quality, but not as comfortable long term - I think it's very personal matter.
I'd recommend you to check out Senhessier HD600 and maybe 700. Also Beyerdynamic DT 990 (32 or 250 ohm versions - get 32 if you ever would like to use with mobile device like smartphone or headphones out port straight out of laptop), if you connect it to your denon - you should go with 250ohm version.
Pro will have tighter fit, coiled cable and a bit cheaper materials, otherwise identical sound.