Got the KSC-75 today and have been spending some time listening + switching between this and the AKG K 314 buds that I so love.
I paid about 20 euros in total for the KSC-75, and for that price they really aren't bad. For the K 314, 6 euros + shipping, and for that price they are awesome.
First, it has to be said that I got rid of the foams for both the 314 and 75 in short order. Both phones sound too dark and bassy to me with the foams; ewwy. I have no idea how I'm going to protect the 75 drivers without the foam around, but... no big deal for now.
I haven't heard the higher-up Sennheisers, like the HD600, but the descriptions I've read about them – slight veil, smooth, laid-back sound – aren't too far off the KSC-75 as I hear it. Smooth and laid-back, definitely. This is a bit strange considering people here have been comparing the 75 to the Grado lineup, i.e. aggressive sound. The K 314 buds are considerably more in-your-face than the 75.
Switching back and forth, the 75 can make the 314 sound a slight bit cheap, but on the other hand the 314 are more energetic. After only a few hours, I wouldn't quite say which one I think is better. The 314 are, in my opinion, a bit better for classical as well as metal, but for mid-tempo indie the 75 aren't too bad, and in any case they are more mellow so I suppose they would do well for mellow moments.
The 314 only weigh 5 grams, eight times less than the 75. Still, the 75 aren't too uncomfortable either; the ear clips can be bent to fit ok. I prefer the 314 for comfort, but I guess you could say this about most any earbuds vs. bigger clip-ons.
In any case, for me the KSC-75 sound quite smooth and laid-back. Not bad at all for the price.