We have fallen in love with Anastasia (American pronunciation) if we are having a girl. We will call her Annie. DS is Theodore nn Teddy and our last name is English, two syllables and ends with "men."
DH really likes long names. He absolutely love Anastasia Catherine. Second for him is Anastasia Josephine.
I like both, especially Anastasia Catherine. I don't mind the length but I might want to keep Josephine around in case we ever have 2 girls, though the lead for that is Margaret.
But because I believe in due diligence I have to get other opinions. Here's our list of possible middle names, feel free to give suggestions. Partially at the root of this is the issue of using a name that we love as a first name but this might be our only chance of using it at all. Ideally we want 3 or 4 kids.
Catherine
Caroline
Claire
Elizabeth (also a possible option if we ever have 2 girls)
Faith
Grace
Hope
Jane
Joy
Margaret (lead if we ever have 2 girls)
Patricia (DH's mom's first name. She was known to some in the family by her middle name, Ann though. DH thinks Anastasia is enough.)
Rebekah (one of our favorite girl names that we've had to table as a first name)
Virginia
Re: MN for Anastasia
I don't think Catherine or Josephine is too long with Anastasia and a 2-syllable LN. I like most of the options on your list, though.
Since there isn't a pressing family tie, I would probably avoid Patricia, Rebekah or Virginia so you don't have the -a endings on both names.
I agree it is tough to decide when you aren't sure you will have another chance to use other names you love. I guess I would try to weigh if you would be more sad to not use it at all or if you used it as a MN and can't use it as a FN later if you do have another girl. We had this issue with DS's MN. We decided to go with the name I liked a little less and to save the one I liked more as a possible future FN. But I am far less attached to the boys' names on our list...