i have the 6.0 and i have straight pipe and it sounds good. I am looking into going to a larger size but it gave me a nice tone without dropping $400-$500 the day after I spent $40,000.00 to get it home. When I am on my truck hard the tone in very nice if I am in a nice residential neighborhood I can take it easy and noone hears anything. Banks systems do sound very good a friend of mine has the full banks system and there is a noticealbe difference. Good luck in your choice!