You will also need a 4 ch transmitter/receiver and the tamiya battle unit for that King Tiger. Around another $200. Probably looking at $600-700 when said and done with that KT if you need batts and a charger as well.
Taigen will start off much cheaper but if your planning on doing IR battling you'll have to upgrade the control board and install a battle unit as well as a Transmitter, receiver, batts and charger. Will end up being around the same $$ when done, but the tamiya KT is more set up as is for IR battling so less wrenching time spent.