You would only need that kit IF you dont have the factory brackets from the factory radio. You can get these brackets from your local Toyota dealership. With that faceplate kit you dont have the option to have a pocket underneath the radio. I would suggest using the factory brackets with a universal pocket underneath the radio (if you go with a single din aftermarket HU).
You can use this kit if you want to go that route. It may still be easier and cheaper though to use some ABS plastic to cover the gap left under the radio. You can cut through ABS pretty easily and mount different things to it.