Exhaust question about my ninja?

my exhaust tanks are pretty beat up and dented on my 2001 kawasaki ninja zx600, its a duel exhaust and i am going to put on two of those exhaust tips that you see on hondas and such, now, ive heard all kinds of different things, back pressure and baffles and such, i went to an exahust shop and they said it wont hurt the bike at all as long as i keep the pipes the same lengh or maybe extend them a couple inches. now, ive seen these choppers and such and they have just straight pipes all the time, is there a difference between mine and theres besides the normal things, will it sound like an indy car or something? im tired of the quiet exhaust and cannot afford another preformance one, Loud Pipes Save Lives ive always said. opinions plz, knowledge is power