I used a pair of HD 280 Pros for about a year before I got my 558s, and I have to say, isolation is the only area in which the former outdoes the latter; in par

I used a pair of HD 280 Pros for about a year before I got my 558s, and I have to say, isolation is the only area in which the former outdoes the latter; in particular, as far as comfort goes, the 280s made me feel like I was wearing a bench vise on my skull, while the 558s sit so lightly that I barely notice I'm wearing them at all. Since I was working in a cubicle environment at the time, I figured I'd keep the 280s at work, primarily for their excellent isolation, and the 558s at home, where I maintain a quiet environment in which open headphones' lack of isolation doesn't pose a problem. That lasted about a week before I started carrying the 558s to work, because I could simply no longer stand to wear the 280s. It really is a shame the 280s are so big and clunky, because they are, as you say, quite good headphones otherwise, albeit IMHO a little weak in the lower part of the frequency range. HD558s being as cheap as they are, and from all I can gather being also the price/performance sweet spot of the Sennheiser 5x8 range, my experience leads me to suggest that it'd be worth your while to consider picking up a pair. (And I hear elsethread that the 558 foam mod makes them effectively indistinguishable from the twice-as-expensive and even more neutral HD598; I can't speak to that from personal experience, as I have yet to do the mod, but if true then the HD558 is most certainly the standout performer of its range.)