i have a question. from what everybody says from doing research, aftermarket exhausts don't really give anymore gains than the stock exhaust. so, if i was to get a dc header, could i use it with my stock exhaust or would i have to get an aftermarket exhaust? i love the sound my exhaust gives and if i don't have to change it, i'd rather not. is there any size difference between, let's say, thermal classic and stock? am i hearing wrong and paying $500 for a thermal exhaust well worth it? thanks!