I put the round Indian HiFlow air cleaner on mine, along with the Stage 1 pipes and slash cut tips. Those two gave it a nice low rumble.
I then put in Lloyds 558 cams and had it decatted. The noise rose in volume and pitch from a low growl to attack dog snarl, which some people like but I found too loud and aggressive. I swapped the decatted header for a standard one with another forum member. He likes the extra noise and I like the return of the quieter rumble. The 558 cams still give it a bit more exhaust presence over stock. The fish tail tips always seem to me to be a higher pitch than the round tips, as if they have a tingy sound to them. I've heard similar comments from others, so it's worth listening to a few other bikes for yourself. And I'm probably clumsy enough to give my shins some serious damage if I had fish tails, they seem to sit further from the bike.
From Woodrising (no, nobody else has heard of it either) Rides a Springfield Dark Horse