I have a catless downpipe, and gave the sport exhaust a try... 2 hours later I got back to the shop and told them to take it out of the car... The only thing I liked was high rpms and the burp when you change gears, really awesome! BUT, for daily driving, in the 2-3,5k RPM range it was just impossible to use... It was too loud and the drone was terrible. I was told to put some more resonators, but the noise really isn't for me.
Just the catless DP already gave the car a different sound. I also felt a little less low end torque.
I just disabled the valve and now the car has a good sound, and a little burp in gear change... Now I'm happy.