Hands down Bassani!!
When I was trying to decide on an exhaust system I took a trip to my local speed shop, All Mustang Performance (
www.ampperformance.com), and asked them what they thought. Jason proceeded to school me on exhaust and took me for a ride in his 2001 GT with Bassani Cats and O/R X-Pipe. That ride about shattered my teeth, then he proceeded to give me a ride in a 2001 SVT S/C (Novi 3000) and I was hooked. There is nothing that sounds quite like Bassani, just plain nasty.

You can always tell a Bassani system
Some draw backs are that it is a bit costly but you will notice the quallity during installation. Also, nobody wants to race. However, when I cruise through the parking garage at work there isn't a car alarm not left chirping.
I was also able to install the system myself using common hand tools and with minimum tweeking was able to allign the rear tailpipes. Installation took half a day.
The pipes feature a 3 1/2 inch polished tip that runs deep under the car (looks good from the side) and I believe 2 1/2 inches to the glass packs.
If you decide to go with this system call AMP don't order online they will give you a better deal. They're price was almost $75 less than the best price I could find.