I really like Allegra from your list the only one I really didn't like much was Clementine (we have a cow on the farm called that and she is a pain ) but WOW your list is massive I don't feel so bad now
my favs on your list are Peyton and Samara. and i think of those too Samara goes lovely with Imogen.
i would take off Abigail and Allegra based on you not wanting to have a Immy & Ally or Abbie.
i would take off Rafaela it is a bit close.
I like Samara the best it is s beautiful name and it goes well with Imogen as a bonus. I like Clementine too but doesn't sound as good with your DD1. Layla and Lyla are nice too. I don't like Allegra and Rafaela, sorry.
Cadence (love it with a K)
Peyton (what about Peyson/Payson, i think thats gorgeous)
Seraphina (we very nearly called our dd this but ended up naming her Sapphire)
Temperance (love this, love names like this)
Samara (i do like this name)
Those are the ones i like from your list, just thought i would suggest Vienna too. Its nice and pretty but unique, i have it as one of my dd's middle names
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