Speaking from personal experience, I've had dual OBX mufflers/axleback exhausts on my AV6 and they sounded nicely deep but fairly quiet. The AV6 is a very quiet car in my opinion.

Anyway, it was well worth the money and everybody thought I had Greddy Evo's because it totally looked like it and sounded like it (but quieter). I didn't see anything wrong with rusting or anything. It was clearcoated and stainless steel + I had a good installer do it so it didn't have any problems.

Of course, it would always be good to go for some name-brand exhausts so that you can say "I paid $300 more to say that they're made by Greddy." (I would). Anyway, don't worry about the exhaust too much. It doesn't give you that much gain anyway. Especially for the money invested.