I think reading Steve's Bolt on guide is required before posting on this forum ;)
If you get a header, you will have to tune it to remove the CEL and get actual performance out of it. OP/FP will do little to nothing as far as performance.

Get a UEL header and tune it with open flash

I read over steves guide as recommended. It was very informative so thAnks for that.

It now seems like you would just advise to get a catless header plus tune over catted header, op, and catless front pipe.

However, I feel like a catless header will be much much louder than if I did a catted UEL one combined with a catless front pipe. Seeing as how I want some increase in noise, not bleeding ears loud, what do you think? Keep in mind that I'm using the greddy axel back with way as that's the whole point to this vs just buying a new cat back.

@geruta

I have the same exact set up as previously mentioned: Tomei UEL Header with stock exhaust except for an aftermarket axle back that's a Greddy SP Elite Clone. In my honest opinion, it's a little too quiet for me. There's enough burble and growl upon acceleration, but not enough in cabin noise. Most of the noise from this set up is behind the car, which is a great thing for the more mature crowd. However, I think with this set up, mated with an aftermarket over pipe and resonated front pipe, it'd give it a slightly more volume that it needs. As for myself, I'd rather not spend more money than required for my desired sound decibels, so I opted for a muffled track pipe for the extra burble.
Here's a sound clip of my set up. You're welcome. :bonk:
[ame="https://www.youtube.com/watch?v=eoJ1UzHPHGY"]Subaru BRZ Top Pro 1 Speed Axle Back Revs - YouTube[/ame]