The chain reaction header that is soon to come out will be the best header for the S3, without any doubt. It will also work with almost any slip on system that fits the stock header. So pick an exhaust system that looks good to you, and get a CR header later and you won't be disappointed. A dual can setup is gonna make the most power, period (its been proven). However, many think that a low single can looks much better (including me), and it does cut some weight off up high where it makes a difference. I swear I can flick the bike side to side faster than before, and the front to rear balance is better. This for me is reason enough... A dual can system is going to sound deeper, and most likely quieter than a single. I love my Zard, and plan on modifying the header shortly, then getting the CR header later down the road. What EXACTLY do you want in an exhaust system?