Unless you want the best overclocking performance, I would get a B450 mobo and save a few bucks. I would also go with the normal r5 2600, not the x version since everything I've heard says that the 2600 overclocks about the same as the 2600x. If you don't plan to overclock then r5 2600x is fine since it will be faster out of the box. I also recommend RAM with at a speed of at least 3000 MHz. Memory speed affects Ryzen a lot and faster memory will improve your experience with Ryzen. Other than that, everything else looks good.
I forgot to mention, you may want to wait before pulling the trigger on this. AMD may be announcing the next generation of Ryzen at CES and if the rumors are true, there will be massive performance gains (although I am a bit skeptical).