FRICK! Those calspeeds look pretty good, I've read good reviews with OBX's except the welds could be a little nicer. I myself went with Pacesetters, I am regretting not getting stainless :/ I think Pacesetters stainless were about 4-500? Mine fit wonderfully, when doing headers make sure to use some good think copper gaskets to prevent leakage, install following directions and than recheck bolts every few trips. Also while ordering pay attention to if they have egr port, o2 sensor bungs etc etc.
I posted a thread with my whole new exhaust setup with a video if your interested. A y-pipe doesn't necessarily restrict flow, just converts dual into single exhaust for easier routing and less piping.