Notes about the exhausts:
The Stage 2 is only cheaper is you can do it yourself, and then only a few $. Are you comfortable cutting the diffuser? I'm not, but many are certainly capable of doing it.
The QS is lighter, might be a tad louder than Stage 2, and definitely makes more power than stock. I'd like to see Stage 2 dyno'd; I don't think I've seen a comparison against the other options. Both sound great.
Stage two seems to be having a weld issue with a bracket, too. The QS is still pretty new and could also have some quality problems, although none have shown up yet.
Since the noise issue came up, let's also point out that cutting the diffuser for the Stage 2 technically takes your car out of stock class for SCCA purposes.
Stage 2 tips point down, QS point out. Pick your preference. I picked QS because it was lighter and i thought I could put it on myself, which I did.