I have three pairs of headphones: Sony 7506 (closed back), AKG K501 (open back), Etymotic ER-6 (in-ear).
I love the ER-6s for riding my m/c and situations where I want to block out external noise, e.g. planes, trains, and automobiles. Probably not applicable to your uses.
Before I lost (stolen, I suspect) my 7506s I used them at work. Can be driven nicely without a headphone amp. Not nearly as comfortable as the K501s, for me - while circumaural, they don't quite fit around my ears. I find the K501s sound significantly better overall, but that's in part due to their open vs. the 7506s closed-back design. Certainly not bad sounding, and the closed-back helps insulate your co-workers from your tunes - which is why these are the 'phones I used at work.
I loooooooooove my K501s. Tougher to drive - portables won't cut it without a headphone amp like the Airhead. Supremely comfortable circumaural fit, great sound IMO across the range though a bit light on the bass.