Buying the Klasse twins or just the sealant glaze is optional since the Megs kit inclues a finishing wax which gives protection.
One thing to consider is that the DA finishing wax has some cleaning power so if you plan to use the Klasse Sealant Glaze or combo (I personally like to use it in combo but using the glaze by itself is possible since you'll be correcting the finish with the DA compound), topping it with the DA wax can affect its durability, so an option could be to purchase a pure wax like M26 or Collinite's 476.