|After doing some quick research, I'm finding that you may not be comparing apples to apples. the information that Speccy is giving you i believe is the I/O Bus Clock. The information that you are seeing on the website you linked in your post is showing you the Data Rate.|
According to Wikipedia, the two different memories are the same, you're just looking at two different pieces of information.
666.66MHz(I/O Bus Clock)=1333.33MHz(Data Rate)
Long story short, I think you'll be just fine.