i cant find a place to get the rx kit and the only one ive seen is like 170 and the rs is 129. thats a pretty big price jump just for a rad.
It's worth the money. Get a thicker and better rad to start out with. Not only will it give you better temps but you have upgrade options if you ever want to include a GPU.
Edit: Heck, while you're at it you might as well get the RX360 kit--it's $10 more expensive (why, I do not know)