Hi flow cats are $100 or less, metalcore cats are like $120. I had a hi flow on my NA set up and have a metal core for turbo. For NA, it did help with sound in my case, and I live in an emissions county. I also park in a garage, and letting the car warm up for a second without a cat can really leave the place smellier than no cat.

They also sell "non" or "anti" catalytic converters on eBay, if you did live in emissions county. It's $40 or $50 and is a straight pipe with a cat casing, nice for turbo set ups that don't want restriction. Lol

If you're NA, a cat won't rob much power, helps give a nice tone, and doesn't kill the people driving behind you. Then again, I have a cut out for when I want to bypass my cat. Lol