I recently bought a 2001 Sentra SE 2.0. I was wondering if anyone knew if it was better to buy the whole Cat-back system or just get a universal muffler. In the long run i am planning to replace the headers and the cat. What would be my best step towards doing that and/or what order would be the best for doing so? ex. headers, cat, cat-system. thanks.

buy a cat back, no doubt
the stock piping is so small and restrictive that the 150$ muffler will not add much but noise
when you can spend 5-600$ and get noise AND power.

any order you do it in would be about the same