The Dinan exhaust is desgned for the stock cats and resonators. Someone about two years ago added a xpipe to their dinan exhaust, and it sounded terrible (he was trying to sell the exhaust on the board after about 2 weeks of having) until he replaced the xpipe back to stock. I don't know about how the ss headers would sound/perform w/ the Dinan exhaust, but I don't see you getting a lot of additional power with the xpipe or cats once you've done the headers.
"Control, Vision, Determination" These are the three fundamental components of the new generation race car driver!! SPEED is a by-product! -Memphis Raines