Personally, I would go with just the Kingston 8GB and leave the other 1333 out. 8 GB of RAM is usually more than enough unless you are doing some extreme multi-tasking.
But, in the light of that, no it won't hurt anything and you could probably utilize all 16GB but at the slower speed. You should put the slower RAM in the first set of slots and the kingston in the second set. This will allow the memory controller to set the speed for all 4.http://www.tomshardware.com/forum/253369-30-sizes-frequencies-advisable