Thanks for your reply Armaegis.
However, I should have made it clearer in my original post ... sorry about that ... but I already have a pair of headphones for my workouts. I use a pair of Sennheiser PMX 680's, which I love.
I am now looking for a pair of portable, over/on ear headphones, easy to drive, with strong isolation, that I can use primarily on my commute. I guess one additional requirement to add would be comfort - for extended listening time.
With that in mind, what would you suggest I look into?