My Ultimate Ears Superfi 4's broke the other day and I'm looking to buy a new pair of earphones. I liked the UEs since they fit very well, were portable and isolated great but they didn't sound very good (i never changed the tips, but i just learned about that reading these forums) and were too midrangey for me. I've heard a lot of great reviews about the S4's sound quality but I was wondering if anyone out there could tell me how the isolation stacks up? I live in a city, walk next to highways, ride the subway and whatnot frequently so good isolation is one of my top priorities. If anyone has any good-sounding and isolating alternatives between 50-100usd, I'm all ears as well. I listen to a variety of music but I generally prefer a clear balanced sound, not too bass-heavy.