Each box card surcharge is not the effect of the 1 + 1, but multiplies the possibilities. already because the cards have a slightly different universe and especially every time, keeping the original spirit a little anyway. So each card of each extension can be used if it agrees with what the leader said that of course ... The only downside would be the price of each extension, but given what it brings to the game, seen the quality cards every time, I can understand.