New catalytic converter needed?

Any advice would be greatly appreciated! The check engine light on my '99
Accord has been going on and off since 98,000 miles and I now have 132,000
on it. Autozone checked the error code and it was code 67 - catalyst system
efficiency below threshold. Performance and gas mileage was unchanged so I
decided to live with it. The light now stays on and I occasionally pull the
fuse to clear it but it comes back on after a day or two. The car is still
running great but I need an emissions test in January and they plug into and
check the code data.

Honda wants almost $800 just for the cat. I see there are a lot of online
auto parts stores selling direct fit cats for the '99 Accord EX 4 cyl at a
price range from $112 to $248. Any experience and recommendations??

I also read that in a lot of cases it isn't necessarily the cat. I did
replace the gas cap just in case and a friend checked the O2 sensor and said
it appeared to be ok. I did check and was able to remove the existing O2
sensor. I'm not sure if I should just try a new sensor first or just order a
new cat.

Thanks in advance for any advice.
George