out of the box I think CKM500 are a bit warm with more crisp highs but after burn in they will be a bit more dull as the bass gets stronger while everything else tends to smoothen out.
unfortunately my CKM500iS I had them in my pocket quite a bit and the earpiece plastic section came off from the coloured section. I'll try krazy gluing it again. I did buy a backup pair in Taiwan (just CKM500 without the mic/volume box), but these were in my luggage and I was on the plane when I found out my iS broke. As a result I bought the cheaper CK323M during a transfer stop in Japan (500's weren't available, only some newer ones like the 55x and 77x). They have a very different v-shaped signature with recessed mids and mid-bass. That might change with burn in. The highs seemed more crisp and clear than the 500. I like the flat cable of the CK323M's and it comes with a cable winder but unfortunately it leaves some dents on the cable where you clip it on. They are rather tangle-resistant and also have the small plastic ring to bring the left and right cables higher/lower together, unlike the CKM500.