Congratulations on your little boy! My favorite from your name list is Caleb Briggs. I really love the name Briggs and Caleb goes best with Joshua and Abigail. I do agree that Ian Allen sounds like Ethan Allen.
Also, I'd stay away from another "A" name. I know too many sibs that resent their sibs that have matching first letters. It makes them feel different or left out.
Well, it took us longer than I ever would have imagined, but we finally decided on.... Ian Briggs. Though Philip Briggs or Raleigh were perhaps the best combos phonetically, DH disliked the nicknames for Philip so much that we had to mark that one off, and then it was down to Caleb and Ian. The little guy just didn't seem to be a Caleb (somehow we both pictured a super tough mountain man type, and the little one has a gentle spirit), so Ian it was. DH was not disappointed; Ian is one of his favorite names, and we love the meaning "God is gracious." I'm conscious of the -en, -en ending, but OK with it.
Thank you all again so much! It was terrific to bounce things off a wonderful group of name connoisseurs. :D