For the kind of sound you're looking for I would go with one of the 20" dynomax super turbos.

I think you might enjoy an H pipe a little more than an X style, although I prefer the sound of the X style, I always thought it sounds less old school than the H.

Coming off the collector, Flowmaster sells a reducer cone that drops in size a little more gradually than the norm. It might be a good idea to try those.