I just got this finished:
The mufflers are Full Boar single chamber; the tubing is 2.5" mandrel bent stainless from the cats to the mufflers, and from the mufflers out.
The older cats and headers are are 100 cell Mandrel Bend Solutions cats welded into Fabspeed bypass pipes. The headers are the cheapo Chinese ones.
For the mufflers and pipes, I paid $165 from Performance Curve in Roanoke VA. A local muffler shop welded it up for $150.
This setup replaced a Borla Boxster S muffler. After just a couple of days of listening, this setup seems quieter but deeper at idle, quieter with less resonance at highway cruising speeds, but louder/deeper at WOT. Hopefully I can get some dyno numbers with the new system.