The sales of all of the companies put together is about 800 million dollars. Here's a list I've found of the major exhaust after-market companies. There's dozens of different companies and of course Aero didn't even make the list: http://findarticles.com/p/articles/mi_m0UDO/is_18_14/ai_75179174
Aero doesn't make a complete set of after-market products -- no manifolds, etc. They don't handle many different car models, neither my late model supercharged Impala 4-door or my BMW convertible is listed in their vehicle search.
Aero's compeitition has huge catalogs of their offerings. The tiny Aero Exhaust doesn't even have a catalog of its products on its primitive website.