I apologize if this question has already been answered. I looked but didn't find anything anywhere on the googles or in here about it so here goes:

I own a 2000 Civic Coupe (EJA) that is in need of an exhaust replacement.

I've settled on the Yokana Catback and a Megan Racing 4-2-1 Stainless 2 piece Header.

The Megan has a 2.0" outlet.
The Yokana has a 2.5" inlet

I know i need to purchase a high flow cat but i'm not exactly sure how to get around the differences in pipe diameter as described above.

Do I have Compatible flanges welded on for either end of the cat?

I'm thinking it's probably a good idea to buy just the header and exhaust first, get them installed, then figure that Cat thing out later.

Any assistance would be greatly appreciated.