Here are a couple of a porsche with a Magnaflow and Ansa. I know that it is not an xfire but I think that these two show a bit of the difference in the harsher sound of the magna vsersus the ansa. It is of course up to the owner what sound they want and this may help with decisions based on the amount of volume/rumble that you want:

Magnaflow:

http://www.youtube.com/watch?v=vCmqT...eature=related

Ansa:

http://www.youtube.com/watch?v=K_-uguHqTqc&NR=1


Oh and if you wanna get crazy here is a flow master which I personall do not like:
http://www.youtube.com/watch?v=iDzS6...eature=related