With all this KSC-75 love going around, I pulled my pair out (been using SR60's lately), and hooked them up to my iPod mini. No amp, just the simplest of setups. I hit "shuffle songs" and have been listening for a couple hours and every style of music - whether it's funk, metal, rock, r&b, or anything in between (bjork, prince), and all of it sounds better straight out of the iPod mini's headphone jack that it does amped with a Porta Corda II through SR60's, DT770-80's or HD580's. The best balance of nice warm bass, detailed, but with enough high end and mids. I can hear just as much detail as I can with my other cans when they are amped.
To my ears, it's just the perfect fit. I think it's funny that I've got $500-600 worth of headphones and a nice portable amp, and what sounds best is a $15 pair of headphones. There's something about it all that really scares me. All this headphone and amp owning, and I always come back to the same family of Koss drivers for the sound that is the best for my ears.
I've really been wanting to get back into another hobby of mine (guitar playing) and have been financially strapped from doing so. To think I could get a decent guitar and amp, AND still have a headphone setup that sounds excellent to me (and not just "good", but the best combination out of the stuff I own), it's very tempting to ditch it all and just start playing again..