Stage 1 pipes don't change the sound as much as some of the better aftermarket pipes do honestly.
I went with the RPW Slash pipes on my 07 Hammer S and love them. 2-into-1 pipes hopwever produce more power (about a 5hp gain), so if performance is more important than sound to you, look into a 2-into-1 pipe like the Big Slash or something similar.
The best sound, bar-none, is the Hard Krome Sideburner, but it's not the most aesthetically pleasing. It is the only pipe that drops the exhaust note to a deep rumbling, musclecar sound. Any other pipe made has a smaller diameter, and can be a bit raspy.
My personal favorite (and the way I'd go if I were doing it again) is the Conquest Customs "Octanes". But you'd better enjoy LOUD.