How much do tubes affect how your amp will sound? What makes them change the sound?

Right now I have SOVTEK 588 in my Fender Hot Rod, but I bought it used and this is what the guy put in it. I would like to switch back to the Groove Tube 6L6, EL84, or KT66-HP.(All Groove Tubes)


But if there isn't much difference between tube sounds then I won't bother.