I'm going to disagree a little. Granted, I have had the good ol' MBRP flexback on my focus for going on 5 years, but I have installed several ebay catbacks for people and they have been of suprising quality. Usually just made by exhaust shops looking for some extra income. Just know that if the ad says stainless the flanges probably arent, just the piping. And if an ebay ad doesnt answer a question about the product, its probably a bad answer.
"Every time something good happens to me you say it's some kind of madness. Or I'm drunk. Or I ate too much candy."