yaleboyDoes not compare... different presentation and STAX is much more preferred to me. The Koss is much more rolled off at both ends and lacking in low end compared to the L300 and is flatter sounding. L300 is much more dynamic and impactful, with some of the best bass I've heard (properly amped beyond the STAX SS drivers). L300 is also quicker and more detailed sounding. Koss ESP950 absolutely needs low end EQ, L300 doesn't. Think of the Koss ESP950 as an HD6XX with much less bass (HD700 has noticeably more bass and it's a little bass light...) and the STAX being a Focal Clear.... very different. Once I picked up an L300 I had no desire to listen to the Koss ESP950 at all anymore...and I really liked it before the STAX L300 came in.
Helps when you can drive the ESP950 off a STAX driver, but it still lags way behind the L300.