I checked both E-80 and E-60 at Frankfurt Musik Messe and I can say that the difference in sound quality is easily appreciable (even if not so big, especially for some specific sounds that should be exactly same).
There are some other differences that should be considered, as the multiple MFX, the vocal input (with effects and harmonizer) and the powerful on board amplification system that E-80 has.
Up to you if it is worth the difference in price.