If you are looking for louder then you will definately want an o/r mid pipe (no-cats) . The X and H pipes make similiar HP #'s with the X-pipe making a slightly higher pitched sound . The UPR x-pipe is a nice piece and one of the cheapest I've seen . BBK also makes a nice one .

If your concerned about money and just looking for sound then you can get by with your stock headers . The after market mid pipe will bolt right up . A nice cat back would really help out . Magnaflow , Flowmaster , and SLP make nice "loud" cat backs . Or to save money you can just weld in some 2 chamber flows or some magnapacks to your existing factory cat back .

I will be changing my exhaust set-up shortly . I will be going with the Mac Pro-chamber mid pipe with a Flowmaster American Thunder cat back...I've heard it on another cobra and it sounds awesome .

Let me know if you have any other ?'s