I just saw that you live in California, I live here too. To give you a heads up, there is no substitute for the catalytic converter. If you look at all the websites, they all say excluding California. We have strict rules here buddy, it will not ever happen.
I have an illegal header on mine, when i get a ticket i have to go to the state referee, and make everything stock. then i have to put everything back. If you end up going through with your plans, you might have to by pass the state inspection and just pay the fine, anywhere from $300 to $400, depending where you live. Mine was $350 in Los Angeles.
Also, it is not worth fixing up a hx. I recommend leaving it stock and selling it. Buy a different car and then fix that one up.