Playing good progressive music is just like any other style or genre. You need to have your techniques down (legatto, alternate picking, sweep picking etc) and you expecially need your own defined style. You don't have to know all about theory to know the fretboard backwards but you do need to know your way around the neck. 'Prog' is just about thinking outside the box, it all depends on what music you like to create and what you play. You can stick a label on pretty much anything, the most important thing about getting there is knowing your techniques, having your own style and knowing the fretboard. For me, I never plan out a track or know what I am going to come up with, I just play, experiment and most of all hear what I want to play in my head before working it out. Different strokes for different folks.