Probably you are right, a solo guitar is not loud enough at the Cathedral, but if they use mic and speakers would be fine... I am going to have a trio of flaute, piano and violin probably , not defined yet but he has a bunch of stuff on Ceremony Music. The provider is Alejandro Villarreal.
I just remember who was the bride using a guitar, it was Jackie PVBride , she got married at Playa Fiesta last february, I havent see her in a while, but I remember I found the name and phone of the provider she was going to use... just cant find it now!