If you want to stay CARB compliant, get eBay headers and relocate your cats in-line with the exhaust. You'll also have to relocate your O2 sensors in a way that you don't get any voltage drop (so you don't get any SES lights), so it may be more trouble than it's worth.
Otherwise, go with eBay headers, put a cat in-line with your exhaust, and not worry about O2 sensors, potentially failing emissions tests (unless you find the right shop :eeps

. Or you can go completely catless and give California a big middle finger.