I agree with you about how
Brynn has a trendy sort of feel when used on a girl. It makes me think of
Bree, and I've heard of a few little girls named Brynlie or something like that. But I do like the combo
Brynn Cecilia. I think
Cecilia is a very elegant name. I associate it with St.
Cecilia.
I see think
Bryn (spelled that way) is nice on a boy though. It's close to Brian/Bryan, so it has the same sort of feel to me as that name does.