If you're going to change the headers you might as well get a high flow cat at the same time to maximize the gains. Toda, J's Racing and Maximworks are best but they are expensive and you will also need to cut the middle exhaust hanger for it to fit the K24a block. It's not as common but this can also cause the headers to break at some point, esp around the flexpipes. I know some people who have experienced this issue.

Of the ones selected, I would go for the Comptech one (CT Engineering). They are a pretty reputable company and many TSX/Euro owners have this installed without issues.