Yes, you must change your motherboard. The i7-2600K uses the LGA 1155 socket. Haswell CPUs such as the i7-4770K use LGA 1150 which is not compatible with LGA 1155. I agree that the upgrade wouldn't be worthwhile, though.
-What is best in life? -To crush your enemies, see them driven before you, and to hear the lamentation of the women.