The upgrade bug is what it is, an ailment. Once you get it, depending on how severe the case, not much will make you feel well again other than buying something.
Having said that, will buying another Yamaha give you sound improvement? If your current unit is performing within specs, probably not. Good units should be transparent. Invisible. Your current unit is one that should fit that transparent idea. Getting another one, albeit a more capable one, shouldn't make a heck of a lot of difference, if any, to what you hear.
But what kind of AH brother would I be if I didn't help you scratch that upgrade itch? By all means, upgrade and buy to your hearts content. Why settle for a mere or modest bump? Why not really "upgrade" and go whole hog?
Its your money but I'm happy to cheer you on to something grand and expensive.