I have headers no cat and stock muffler. I dont really feel like spending $300 on an exaust system. So how do u think a 40 series flowmaster on the end of my y pipe would sound ?, and just cut off the rest of my exaust.

 

OK now - correct me if I'm wrong, but isn't the 40 series the loudest Flowmaster there is? And you want it to dump basically right under the middle of the car? Well, to each their own, and maybe I'm getting old, but I think it will be plenty loud outside, and the interior resonance seems like it would be pretty annoying too.
Don't get me wrong, I like to hear my exhaust too, but if I were going that loud I would at least get the sound all the way to the back of the car. Just my .02