Doing a cat-back will help some but for the best airflow and most gains you should do the CAI, Long Tube Headers, and Exhaust tri-fecta. You don't really have to worry about upgrading the cats unless they are rusted out or if you just feel the need for all new parts.
I would agree that for their price, the Pacesetter long tubes are a great deal. My exhaust system consists of: Dynatech Supermaxx Long Tube headers into a Dynatech y-pipe with hi-flow cats. This feeds into 3" piping that goes to a single in, dual out Magnaflow muffler (3" int/exh) which is dumped in front of the rear axle.
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