There is no correct answer to this question. Sound is objective. Personally I think the Magnaflows sound the best and all the others suck, but that's just my personal opinion.
I believe the Borla Stingers rank #1 for HP/TQ, the Bassani's & Magnaflows are damn near identical. The flows are the worst for power.
I have the borla cat-back and bassani x-pipe w/cats and listening to an audio clip does not do it justice. If you love that exotic sound like I do, this combo is just amazing when you get on it. The car is definately more powerful. I shat you not- I have had people walking in front of the car jump a foot when I bliped the throttle waiting for a light. It makes old people cry too.
I have a n 03 with Slp headers xpipe and cat back and it sounds incredible with just this stuff it made 430hp and 420 ft lbs. with there tune it made 446hp and 437 torque. with their pulley and tune it made 490hp and 520 ft lbs. It dont get any better than that. all I can say is holy crap!!!!!