As the title says, I'm looking for a pair of portable over-ears with reasonably good isolation that I can use while commuting and at work. Price isn't a serious concern, since it seems like there aren't any summit-fi phones in this category anyways. Until recently, I think the Oppo PM-3 would've fit the bill, but their non user-replaceable earpads combined with winding down production is concerning enough for me not to consider them. What other options are out there?
Best is subjective, and can only be advised based off what you want from a headphone. I can say X headphone sounds the best, and shortly after, someone will come along and say bologna.
Audio Technica M40X is hard to beat on a dollar : performance ratio... The ATH MSR7 is a very, very nice headphone also.
I have Campfire Audio Cascades and I no longer use anything at all. Very musical sound but not exactly reference so if you're bass shy, it might not be for you.