The thing to think of is or are those servos overkill for the king, are NOT what you want or need for the heli.
NOT all servos fit the king and its not all that easy to fabricate mounts for some of them (what I mean is time and effort wise) If they are very small thats one thing but if they are not micro heli size they are going to be a bear to make fit no matter what you .do
You can pick up a new dx7 for under 200$ on ebay from reputable sources and the small 6200 rec is about 50$ without shipping soo those servos included with that radio are about 90$ for 3 of them. Which is a good price for that servo as they are digital and strong servos however you can get a analog servo that is much faster then those and just as strong. If you get that dx7 and you decide that the rec is not what you really wanted or same with the servos you would be out of pocket to replace them with others.
In my own opinion I would op for buying one off ebay and only buy what I know I can use with it and more money I save is more for me to spend on other toys where I have a choice if what I can pick.