So the filters in my ety's (the only headphone i really use) got clogged and i had no more left, so until i could get replacements, i had to pick up a pair of cheapo's so i had something to listen to music with. Found a set of Koss UR55's on clearance at K-mart, and i know from previous experience that koss generally makes good sounding phones even in their lower priced range, nothing to write home about, but they do know what they're doing. Brought them home and started listening and i really like them. They sound very full, natural, and detailed. Perfectly balanced bass and highs, i do notice the lower mids are slightly forward however but it isn't unpleasing. They do sound much better with a headphone amp, i noticed plugged straight into my Optimus they really sounded loose and clunky, coming out of my FiiO E17 they sound tight and responsive.
Anyways, if you're looking for a backup when your stuff breaks, or even if you're just looking for a pair of decent low priced phones, these are a winner in my book.
They are a semi-open design, small, light and portable, just above supra-aural earcup size (they are circumaural, if you have huge ears, these might be a problem). As usual the build quality is very good (koss is pretty good at that). According to some sine waves i tested them with the low end extends to about 25hz before they start complaining. No sibiliance on vocals.