You're right about better flow... even with a questionable set of headers, you're flowing quite a bit better than stock manifolds. In our cars, a better cat-back system isn't even necessary until you get really serious with your mods. After a high flow cat, the stock pipe and muffler are fine until you get well over 300hp.
But if you're looking for the best performance, you want quality headers that will flow as well as possible. Not necessarily a large volume of air, but also an appropriate velocity. Small defects in craftsmanship will hurt velocity and volume, and while the effects may be small, it kills you know you might be able to get a tiny bit more out of your setup.
1997 SE w/SLE package
"White curse? I think it'* more like.... WHITE FURY!" - MyLittleBlackBird