I can only afford one upgrade at a time... and I really need the muffler ASAP.  I want to get the header for next year around this time, is it ok to do that? ÂÂ
Sure it is, but I would do the header first. Running my 2-door with just the cat, and no muffler at all, it still wasn't very loud. In fact, I would be tempted to put on the header, and throw away everything behind the cat.