What To Look For When Buying An Exhaust?

[Jesus954]

Well i aint too familiar to exhaust, when u say exhaust the 1st thing that pops to mind are those loud !Removed! civics that pass by the road everyday lol so im like thats way to loud and it really sounds horrible, But than again i saw some is300 with exhaust that sound just right they are not loud when ur driving at normal speeds but when u push the gas pedal it sounds nice as hell so what i wanted to know is what are the things that i should be looking at when it comes to getting an exhaust? is the only way to hear how an exhaust sounds trough you tube videos? and also would this exhaust mods lead to engine check lights in the future?