Cardigans with a low v cut in front are my favorites for the simple reason that you get the chance to show off your shirt or whatever you have underneath the cardigan. For men who wear cardigans over a shirt and tie probably to the office or some other formal occassion its best you invest in some low neck cardigans.
Feel free to have a tailor adjust your cardigan if its not slimfit for a dressier look. Cardigans available @ Littlewoods.