you have a tough decision on your hands. I'm going to second David's recommendation on the cherry bomb's.

 

Sound quality sucks on my phone so I can't make a decision on the videos but I will say IMO the only exhaust setup that goes on a mustang is flowmaster!!

 

On the 3v motors (2005-2009) flowmasters sound amazing. Even on the 2v (1999-2004) they sounded ok. But I will say the Borla Stingers sound amazing on both the 2v engine as well as the 4v engine found in the 2003-2004 SVT Cobra's. I'm still leaning towards the Flowmaster outlaw since it is a little deaper then the Cherry Bomb's but it is almost as loud if not louder. I still have some time to think. I won't be getting them until next paycheck. So I still have about a week till then. Who knows maybe I will stumble upon some crazy amazing setup before then.