going to be very hard to get a deep low rumble with the V10 because it has 2 cylinders firing at the same time, will always sound weird. You need to get a very large chambered muffler. Flowmaster has a Big Block series muffler, the 70 is larger and quieter, but there is a #50 series that might be what you want. Here's a link to a video of my V10 right after I rebuilt everything without mufflers or cats, just straight dump out from the collectors. Keep in mind I have headers on mine.
http://s655.photobucket.com/albums/u...t=MVI_3195.mp4
I will have my exhaust done in the next few weeks: dual Magnaflow cats, Flowmaster Big Block series 70 muffler, stock dual 2.5" pipes into single 3" out after the passenger tire.