I do not recommend an mSATA SSD; it is older technology. mSATA is has been replaced with M.2. I would recommend a 2.5" SSD. You can move Windows to an SSD by cloning the 2TB HDD.using something like Macrium Reflect Free Edition or you can use Microsoft's Media Creation Tool to create a bootable USB drive to install Windows 10 on the SSD. Since you already have Windows 10 you should not have to activate it after installing it on the SSD. You should disconnect the 2TB HDD after you clone it or before you install Windows. 
After power loss during storm, desktop PC wouldn't boot. Used cloned backup of HDD to boot VERY slowly. Looking at Disk Management - can't see SSD. How do I test status of SSD and if it's working (which it is appears not to be), and how do I resume using it as cache? I'm concerned with messing with Raid settings. Also, if SSD needs to be replaced, what MSata SSD is compatible with desktop XPS 8500? And steps to replace? Thanks!
XPS 8500, 2TB HDD + 32GB SSD