Yet Another Exhaust Question

[SnowSurfLax]

This one's for you true techies out there:

If I replace my exhaust system with a 2.5" from the manifold down, am i getting much bang for my buck?

It seems that I can't find headers exactly made for my QX and I don't have a garage to piss around with to do it and have to pay someone.

So if I'm goign to pay someone to do this, I want to make sure I'm not burning money away.

Thanks!