I would check out Two Brothers exhaust, Yoshimura, Akrapovic, Termignoni, Staintune, Fuel, Triumph standard, Blue Flame, Aprilia, Scorpion, and Leo Vinci.
I chose the two brother M-2 black racing exhaust for my bike. Check out multiple sites online dont just go with revzilla or whatever other site pops up first. The two brothers website sells my exhaust obviously but i found it MUCH cheaper on amazon. Shop around so you dont get boned.