Header, Intake, & Exhaust - bout there

Alright i know wat im gonna do. ive picked out my muffler and im gonna get a muffler shop to bend some tubing.

Only questions are:
1. should i use 2.5 or 2.25 tubin if the inlet is 2.5 ( i kno prolly 2.5 but i didnt kno wat i was gonna do bout the resonator yet)
2 should get a different resonator or will my stock one be fine.
3 should i get a hi flow cat before they install the system or can i do that down the road. ( idk it they will weld the pipe or bolt it to my cat)

thanks for everything

1. 2.25 is the most commonly used size for civic applications
2. aftermarket resonator
3. if they bolt the pipe on with flanges you can do it later down the road with a direct fit cat. if they weld it you can do it later on too, but it will have to be welded on. I'd ask them to reuse stock style flanges where the exhaust bolts to the cataytic converter.

Whoa, whoa... 13 dollars for a haircut AND a shave?

Oh... but I have to pay with warcraft gold? That sucks.