I had a bassani x on my 04 Mach. Sounded amazing.

 

Honestly, save your money and get MAC LTs (amazing headers for the price), pull out your rear cats, and get a chambered muffler like Original 40s (blegh, but they sound nice.)
You seem the seem to want loud and meaty, not loud and racey. X pipes are nice, but they don't have the muscle car growl. Sure, they flow better and you gain a handful of horses, but whooptie-doo. If you have chambered mufflers, get an H, if you have bullet-style, get an X.

 

Shorty headers are a complete waste of money. If you have them, you don't talk about it because people that have read the dyno charts and done research laugh at you. I don't know of anyone that brags about having them unless they don't know squat about motors.
Ford did an amazing job with the stock manifold, shorties don't flow any better (maybe a tiny bit better) than what the car came with.
The whole point of headers is the scavenging effect, shorties don't have enough room to do that.

 

I think it depends on the model. I know 2003-04 have very restrictive exhaust and going with headers x pipe and catback can give you huge gains.

 

I have decided to go with a MAC pro chamber mid pipe with flowmaster super 40 mufflers and 3" tips