The cheapest place to get Charlemagne and Art of War is at greenmangaming.com because they pretty much always let you get everything in the store around 20% cheaper by using digital vouchers available to everyone. Sometimes a little more than 20%. Even brand new stuff like CM and AoW. So prices will be more like CM 12€ AoW 16€. If you decide to pick up something else then vouchers stack with other discounts.