i have an xforce muffler and i have heard a full xforce exhaust on a r33 rb25det and it sounds as deep as you get. Also my dads S15 has a xforce rear muffler and sounds better than quite a few sr's with other exhausts. Even reving it it sounded pretty deep. Definitely not 'tinny'
lol, before i had actually heard these exhausts myself, i also though that they wouldn't sound that great. I was quite hapy to be proved wrong considering the cheap price
Also the stainless steel is 304 grade and a good thickness: you can tell the quality of the steel & baffling by picking up a good muffler and comparing to a cheap autobarn muffler, the autobarn ones are very light because they are thin steel and not very well packed (hence will sound raspy or tinny).