longtubes y pipe and muffler thought?

I want to get a muffler welded in to give it some sound. I dont want to do it twice though.im wanting to do longtubes prolly dt but maybe jba. If I go this route will I need to replace my y pipe? I have a 2014 trd sport so I think I have the 2.5 piping already. I want to get the most performance I can but not being obnoxiously loud and still have decent mpg.
I was thinking dtlt and 18"magnaflow si/so. I will also get some kind of cai not the urd as I like to go mudding. Any help is much appreciated. I want it to be heard at idle but not a ricey aound when im wot

 

If long tubes no modifications required to the Y-pipe. Bolt-on.

If shorties, welding will be required.

 

Y pipe replacement is not required for LTs or STs. The headers bolt up to the stock Y, although the shorties require welding the stock cat onto the shorties. If you keep the stock Y, whether you weld in a new muffler, or put a new catback also doesn't matter.

REality is, whether you replace headers, Y, or catback, order is not important, unless you go custom. Each one can be replaced individually without affecting "bolt-ability".