What someone defines as the various “stages” can vary, but basically:
Stage 1: new air intake and pipes
Stage 2: Stage 1 + new cams
Stage 3: Stage 2 + new heads or rework of current heads
Also, throw in a new ignition system somewhere in with either stage 2 or stage 3.
Yes, there is a huge improvement in performance, but it all comes down to what do you really want to do with your bike verses how much do you want to sink into it.
You may want to check with the dealer about a software download that would help your ECM take advantage of a more open intake and exhaust. Of course, the benefit may be limited jnless you eliminate the catalytic converter.