When people make recommendations, you should examine them with any honest caveats they offer. My caveat: I've only tested two such solutions. But on the other hand, I've used the preferred of the two for about . . . close to three years.
PrimoCache is a Swiss Army knife of caching options. You can cache to RAM; cache to SSD; cache to both; cache AHCI and RAID simultaneously; cache across disk controllers (but -- caveat -- I haven't tried that.)
PrimoCache
I have one system that uses SSD+RAM caching -- running for two years now without changes. The other Skylake system has become something of an experiment for NVME M.2 cache volumes. Because the current setup is lightning fast anyway, I've deferred getting more RAM or upgrading a 2TB HDD to a 2TB SSD.
there are naysayers and skeptics over this and other solutions for workstations. Caching is valued more consistently for servers. I can only say it works for me or continues to do so. the 60-day trial period should give you enough of an idea.