Ive had 3 different x-pipes, BBK, flowtech, and bassani.
The flowtech was the cheapest and had the cleanest tone to it, the flanges were cheap, but if you dont over torque them they will last. I'd buy one again.
The BBK was junk, the thin wall tubing caused a nasty "wrapping" sound between 2500-3000 rpms under a load. Free revving wouldnt make the noise, I wouldnt buy another one.
The bassani is by far the best quality of the three. better sound than the BBK, almost equal to the flowtech, the stainless is great quality and i'd buy another one any day. Both of the ones i bought were used and in excellent condition. I woulndt ever buy a brand new one based on the price though