I have that exact portable set-up with the ES7s, while the isolation is not amazing, it's alright for the commute/office. At risk of sounding like an advert for audio technica or a gushing fanboy I'm gonna say how much I really love my ES7s. They're such a fun headphone to listen to; full punchy bass, slightly recessed mids and clean forwards highs that are never too bright for me. I'd also like to mention how purdy these headphones are, the mirrored cups look very cool in my books. Not heard the 250s, but I imagine they will sound alot livelier and possibly more detailed than the 250s if they have the senns darker laid-back house sound. The ES7s have just been discontiuned, but I think you can still pick them up from retailers and from ebay pretty cheaply (I got mine for £60!). Just be careful about buying fakes, there are alot around (See: http://www.head-fi.org/forum/thread/417148/ath-es7-buyer-s-guide-or-how-and-where-to-avoid-fakes)