I think the best overall pipe for street use on sport bikes, is genenerally an Akrapovic. They are not overly noisy, and most give better torque numbers than other systems. Not usually the best for peak power, but a wider overall power band. A more usable increase that's well suited to a street bike.
2nd in my book would be the Muzzy system. A little better peak power than a Akropovic, but a little less "grunt." I've got a lot of experiance with Muzzy systems. You can't really go wrong with them.
If peak power alone is your goal, you might like the Hindle systems. Kind of noisy though.
Don't have a lot of experiance with Two-Brothers, Yosh, or many others.