Parts replacment question?

[240sx2soon]

I realized recently that I was going to change my plans for putting an I/H/E on my stock 96 Se and just stick with suspension and brake mods for now. But after I developed and exhaust leak ( which I later found was a split pipe just behind the muffler) I was thinking more seriously about replacing the whole exhaust system. I was trying to avoid doing this because I plan on swapping out the motor next spring to an SR but now that the exhaust has to be done I figure why not, I will be able to use the Apexi GT spec for the turbo set up as well as the high flow cat. So the only thing I really would need to sell is the Header. Is there any real performance gain with the upgrades I just mentioned? My engine sounds raunchy right now and it definetly sounds like it needs to breath better and rev freer.