I was worried about the exhaust being too loud on my car too, as I had to dump before the axle as well. Not as much engine as you, but I went with a full 2.5" system I made up from scratch pretty much using an X pipe and Spintech side exit mufflers. I am still making the tips for it (which will be angled back and end right under the sill infront of the rear) but here is how they sound..

http://www.youtube.com/watch?v=CK6qKTXjJKM

As well, I mocked up a tip on one side and it makes a very noticable difference with about 10" of tubing out of the muffler. This is inside the garage too...with it outside, you can hear it enough, but not too loud at all I think.


Here it is with the mounts all done and painted by the way...