If you own more than one of these Koss PortaPro/SportaPro KPH30i KSC75 KSC35 KTXPRO1, it will be nice to hear what your liking order is (and why if possible) and which one you grab the most often from them. I have all of them except the ksc35 and the SportaPro (since I think it is probably exactly the same as portapro in a different package).
My liking order *as of now* seems to be this (most liked at number 1 spot).
ksc75 - weakest bass of all, but quite detailed (most bang for the buck)
portapro - weakest treble of all, but most non-fatiguing and "warmest", a very satisfying good amount of tight/nice low end bass at the same time not becoming too boomy.
ktxpro1 - good detail like ksc75 but with a better low end, open grill type (may be makes it even more open). seems the most balanced of all as of this writing to me.
kph30i - as bassy as the portapro (may be sometimes it feels even more boomier than than the ppro, which is contrary to what it actually is in frequency response charts), and has plenty of sparkle on the high end too (which is absent in the porta pro).