Besides, most Shure/UE/Etymotic are ugly as hell. Jays makes some sexy plugs, but they're hard to find at any sort of a discount.
Anyway, my two cents. I've only owned semi good sony ex headphones in the past, but others seem to agree with me that denons are hard to beat in terms of value. It just blows my mind that the c551s are so damn cheap and produce sound better than nearly anything that retails $200 or less.
My recent experiences: just had an unusual confluence of purchases during which I brought three new pairs of IEMs into the 'gear' drawer. First bought Super.fi 5 Pros to be the 'high sweat' counterparts to my flagship Shure E500s. Then ordered some D-Jays for change-of-pace and non-over-the-ear situations such as driving. Also, they're very small and can go with me everyday for those 'music emergencies'. That was where it was supposed to stop (for now), however I happened across the IM-716 Newegg super-deal alert thread, and ordered in time to snag a pair of those.
The SF5pros came first. Was expecting a considerable leap from my previous SF3studios, but while they were an improvement it just wasn't that quantum leap I was hoping for. They don't really change (improve) with a better source (the Shures do), they just play pretty much the way they're going to play, which is to say not bad but certainly nothing spectacular. And the memory wire has really turned me off by now.
I quickly re-boxed them in all original packaging in hopes that the D-Jays would serve that role as "cut-the-grass-and-sweat-up-a-storm" phones. They arrived a few days later, and I immediately mounted up the largest tips in the package (huge canals). Took some time to figure out insertion for a good seal but got it done - very experienced in this area. BOOM...to me, much better sound, warm, bassy, highs sparkly but not sibilant, and extremely versatile - you can go over-the-ear or down in front. With my Sansa Clip I can use the short cable without extender and clip to my collar, beautiful. Don't get me wrong, they're no E500 and it's very apparent that you give up extension, detail etc. But they sound plenty good, with no glaring weakness or annoying traits. SF5s were just too vanilla for me, the D-Jays have some panache for lack of a better description.
I started another thread on the IM-716s when they arrived, as they're in their own little world. Having owned the Ety ER4s more than once, I'm reminded of both why I purchased them again after selling them the first time and why I sold both pairs in the first place. The detail and depth/separation is completely intoxicating, and with the IM-716s the bass can be made to have real slam too. It's just that the very thing which makes them a compelling experience also makes them get a little old (at least for me). The beautiful crisp highs become tiring and one ends up relegating the phones to marginal duty (i.e., when you want to take the sip of the sweetest Port wine). No question, an awesome IEM to have, and a joke to consider it's only a $20 investment. Will just be sort of breaking them out from time to time when wishing to sup the nectar of the divine SQ.