there are a lot of other ones that offer a good sound, but everyone's opinion is diff lol. try looking for video clips of the exhaust, i know youtube is full of clips.
this one claims its a magna flow
http://www.youtube.com/watch?v=4AWaxn5nMlw
this one is a berk, they have quite a following of happy customers
http://www.youtube.com/watch?v=9abBL...related&search
the one i have my eye on is the ko racing r1. they have clips of all their exhausts
http://www.koracing.net/movieclips.php
i like single set up look myself, but they have a couple of nice duel setups.
*edit* just watched yhe r1 start up rev video, ohhh sounds so killer.
http://www.koracing.net/viewclip.php?clip=12 
hahahaha