Compared to the Koss SP540: I thought the two would be very similar, variations on a single model, but they really aren't. I got the SP540s and was really disappointed. They sound fine to me, but the fit is terrible on my very large ears and they just feel physically cheap. These Koss Pro4s on the other hand, feel very nice to me. They are heavier, and while that is clearly not as good from a long-use comfort perspective, they just feel more...