You can, but most people use a hard drive just for personal files. This is a place that access times(the huge advantage for an SSD)do not generally help much.
Nothing stops you from doing it and the most common used sections of the drive would make it to the cache.
If you want to upgrade your SSD, you will want to clone windows to the new SSD from the old one. The old SSD can be used with a hard drive(as cache), but may not get you much of a noticeable performance boost.
I would just clean install to the new drive.
It's a better option I think.