Definitley reccomend the HMF, any of those 4 series to choose from. Extremely friendly price but its not cheap made....nice pipes.
Daaang....FMF makes one too. Really good choice too.
Don't forget Yoshimura.
Those are the top three for that 700xx. You should know them. I wouldn't go with the DG exhausts, they're priced cheap....but I've heard bad things about them.