Prog Rock = musical virtuosity, non-standard time signatures, synthesizers, tripped out stage shows, lyrics that go beyond sex, drugs & rock 'n roll, album side long storytelling. The more pure the prog the rock is, the less chicks dig it. Prog Rock is definitely NOT sexy. Play the ladies some Stones if they want sexy.
All late Yes, 70's Rush (Hemispheres, 2112, Farewell to Kings), ELP, King Crimson, Marillion, even some Kansas fits the bill.
Tull? Not so much pure progressive, more like Hobbit Rock. Good stuff, but I wouldn't consider them Prog Rock like the groups above.