I'm sure you will get a lot of opinions on this. I have the Thermal 3" stainless turbo-back and have been very happy with it. I ordered mine with the cat (to stay legal). It is really quiet compared to most systems - it comes with a muffler also. Gains in performance were noticeable and worked well with Stage 1 on my '03. It's kind of expensive but the system is a work of art. I guess it depends on what you're looking for. Quiet or loud, stainless or not, cat or catless. Lots of options....