I like the Duke of Clarence and St. Andrews. They will one day(maybe/probably) live in Clarence House and they both met at St. Andrews Uni. It makes the most sense to me. I can't believe the wedding is less than three months away.
As I learned in this thread, there is already a "Royal" Earl of St. Andrews - it's the secondary title of HRH The Duke of Kent, so his heir uses it as his courtesy title. It's a pity, though.