I agree, if you want to save $ just get the muffler itself, not the entire cat back.
The problem with cat back systems is that people don't realize that in order to get the full potential out of it you have to get a larger Y pipe and a high flow cat. Or if you can get away with it without causing problems with the Feds, gut the cat. If sound is all you want, just replace the muffler.
'11 Ram SXT 4x4 quad cab - 5.7L V8; 128,200kms
'09 Malibu 2Lt 3.6L - 140,000kms purchased 1 March 2019
'06 Pontiac G6 GT - 3.5L V6; 162,000kms (rear ended 15 Feb 2019, and given totalled title by insurance)