From what I hear, most O/R X pipes are the same. But personally, I like Bassani and Magnaflow products. I feel (in my opinion) that you can never go wrong with them but I'll say again, I dont think there's too big of a difference in O/R X pipes
BBK exhuast products fit good as well. The BBK 2 3/4 inch X-pipe in my mind is the best performance mid pipe for use with factory headers on the S197 3valve. You can see how much of an improvment it made over the Pypes on project BOB.