What size diameter cat. converter or resonator did/do you use?

I ask because I'm getting an RSR exhaust for my 92 prelude, and my current resonator's outlet diameter is 2.5". So I'm wondering if it'll be better, in terms of flow and reduction of "bottlenecking", to get a cat converter or resonator with a 2.25" outlet (or 60 mm outlet if those are made)?

Also, how does that work out: bolting up two different size pipings together, so that piping diameter abruptly changes? I'm not too familiar with exhaust systems, so... sorry.

RSR exmag exhaust piping is 60 mm, roughly 2.36" in piping diameter, in case you're wondering.

Thanks in advance.