I love the hollow sound of flowmaster 40s but theyre just too common. I bottomed out crushing part of one of my flows so I replaced them with m80s and love them. Nobody has them, theyre cheap, stainless and sound mean. My top three are borla stingers, flowmaster original 40s and pypes m80s.
But 1998cobrasvt is right, search around on youtube and see what you like. Exhaust sounds are of personal preference, I may like a setup you hate and vice versa. Though you can use our suggestions as a starting point in your search.