I'm old, horsepower was not the ultimate goal for me. Sound level (quiet), appearance (OEM), and longevity were most important in my selection 10 years ago. Longevity meant selecting mufflers that didn't employ "a fibrous packing material" to deaden sound. I purchased the Hall GTS exhaust system.
An aftermarket exhaust system should meet your goals for originality, appearance, quality of construction, performance, sound level, and durability. So before I could offer guidance or thoughts it would be helpful to know your priorities. I'm sure others feel the same way.