I have the Vanguard. It's twin cannister. To me the Vanguard looks more like the Amuse system.
I used to own a G35 with the Amuse Ti exhaust - the build quality is very similar.
Just because an exhaust "looks" similar to another exhaust doesn't mean it is - you have to look at the material, welding and bending.
As for the Agency power, my buddy has the Agency power exhaust on his EVO X - the welds and material are definitely not as good as the Vanguard or Amuse... I haven't seen the Vorsteiner or Meistershaft to commnet...