IMHO.
I've got 2.5" from DP to te Y-pipe, and 2.25" to the mufflers 14851's, no resonators.
If u r not a Bt andu go more then 2.5" u may loose some HP/TQ.
To be honest, when i test drove my car the first time with new exhaust that was too loud inside, no i got used too

))
going with larger piping and leaving resonators is not a really good idea for the sound purposes.
My opinion, get piping done in the way u want it, if it is to loud you can alwaysadd as many resonators as u want.
Good luck, take some videos/pics.