Ceramic just help keep all the heat inside the exhaust instead of under your hood.In some cases yes ceramic is better but not to much in the hp department.More so in longevity ceramic holds up better to heat also good for turbo applications.So price and hp should be your focus.

Molest aftermarket headers(header on a 4 banger)come with a hole for the o2.Some you will have to make your o2 harness longer or some come with a longer harness adapter.

You are going to lose low end tork and gain top end hp.As far as what company to use that is up to you thy are all pipes to me.