Should I keep with what I have, or get an exhaust system?

I just bought a 88 civic to play with. It currently needs a new clutch and master cyl. Right now the muffler has rusted off and has no muffler on it. I don't have emissions here so that is not a problem, but what I am wondering is would it have noticeably more power wasting the money on a whole exhaust kit or would it really not make enough of a difference, if any difference at all if I just keep it the way it currently is. The noise doesn't bother me but since its only got a full 92 horsepower getting a few more would be useful.