The purpose of Intel SRT is to give "SSD-like" performance to a HDD with an O/S installed on it. It's basically for people who can't afford a large capacity (120GB and up) SSD to install their O/S, programs, & games.
So if you're going to use your 128GB SSD as your O/S drive then no, you can't use Intel SRT to cache your HDD.
You'll have to do some research but I'm pretty sure that Crucial's cache only works on O/S drives as well.
So save your money and don't purchase the mSATA SSD.