Just bought the SSAC headers they should be here tomarrow should I

A. hook it up to my SLP catback and delete the cat (then what do I need?)
B. Gut my factory cat (which I believe is clogged but no codes) and put it in the system.
C. Spend more $$$$ and buy an aftermarket cat (whose is best?)

Car is a DD with 145,000 mostly trouble free Mobil 1 (every 4000) miles.