I just put the 19" turnouts like Brent's on my 05 this afternoon and went for a ride. Oh man. First off, they sound great at idle. Get on the throttle and they roar. I think they look good too.
Seems like maybe I lost some low end, but not sure. I may have just been softer with the throttle because they're so freaking loud.

2005 Speedmaster, Tornado Red, AI removed, Uni Pods, JCW 19" turnouts