The gain from the racepipe as you said would be little, but yeh it'll sound nice. Here's a question for you. If you're seriously considering the Cobb donwpipe, why not just hold off from buying the racepipe, since the Cobb dp will replace both of the factory cats anyway.
I know that the racepipes generally aren't very expensive, but when you do decide to upgrade the downpipe (since that is the real restriction), you'll have no use for the racepipe. I would factor in how soon in the future you'd be changing the downpipe to help decide if it's even worth buying the racepipe at all. I guess it all depends on where you want the car to end up performance wise.
Also, and hopefully someone with a GEN2 can chime in, I'm not sure how much you can really change without running the risk of running into fueling problems.
good luck, and happy modding.