Why don't you just partition the 256gb SSD.. say 128gb for OS and apps.. then the remaining partition for games. The traditional hard drive can be used for media and file storage only.
As far as I know, if setup this way, then caching is already installed and activated. I could be wrong but this was my understanding.
Intel SMART caching is something different. This allows the OS to be installed on the HDD but set up it's cache on a small SSD for a perfomance boost. This was of benefit when SSDs where larger SSDs where quite expensive and offered a cheaper SSD solution. This isn't required when the OS is installed on the SSD and is practically a redundant feature since larger SSD prices have been driven down of late.