Acacia - not my cup of tea at all. It just isn't a very nice sound imo.
Jane - nice, uncommon, possibly not that exciting, but a very nice name.
Cassie - it's ok, but I LOVE Cassia, as suggested^^. I'd use Cassia and shorten to Cassie. Cassandra is a bit OTT for my taste.
Owen - nice enough.
Jonah - nice.
Silas - nice.
Richard - nice.
I think Cassia (if you would use Cassia) and Jonah would be my favourites. Richard and Jane are both nice too and you don't hear either of them very often anymore.