If you are POSITIVE that you ONLY want to consider the choices you listed in your original post, I'd go with the HD558, for sure, between the two remaining. It may not have isolation, but if you're going to primarily be using it while say, sitting at home, then taht shouldn't be an issue, and I can tell you from what I heard in the store the other day that the HD558 has GREAT sound. Very natural-sounding.
That being said, don't just discount the Audio Technica ATH-M50x or the Shure SRH-840 in your price range, because they could fit PERFECTLY with the kind of use you are looking for, to be honest, if you're just willing to get away from being stuck on the idea of getting Sennheisers

I've had a chance to listen to both and I'd say they are just as good as the Sennheisers detail and dynamics wise, at least as far as my ears can tell. The soundstage isn't as natural on them as on the HD558, btu the bass has better extension and hits harder. But they have a less neutral freq-response than the HD558, for pretty much the same reason they have better bass. And they do provide excellent isolation from outside noise, which the HD558 don't since they're open-backed.