XPS 8500 PCI-E SATA Expansion Card Compatibility?

I bought 2 SSDs thinking on a RAID 0 configuration for my XPS 8500, after the clean install of W10, and downloading the Intel RST Raid Drivers, I found my R/W speeds were the same, no speed improvement, looking further on the RST program I found my PC only had 1 SATA III port, and the rest were SATA II, I have read that this was a mistake from Dell ( very big one) since my manuals said the XPS 8500 had 2 SATA III ports, so the only option I have is to buy a PCI-E Expansion Card to add more SATA III ports, the question is: Will this work?