well what style hatch are you talking about? either way...Im pretty sure all come with a d series motor...if you can find a 5th gen Si hatch...you would have a motor just like the civic Ex has...not bad power there....throw on some bolt ons and I think you might be happy for a while...but if you are like most...you will just end up getting a B series motor...as far as just throwing on a header and no exhaust piping...dont do that ...that would be gay...way to loud....yeah I guess it would TECHNICALLY give you a little more power..but not that much. just my opinion