If you run Windows in SATA II, the following will run in SATA II mode such as: Directx 11, GPU drivers, internet/wan/lan drivers, audio/sound drivers, virtual memory, online communication headsets & anything else that windows need to run your games. It feels crippled.
"25% OP" seems too high. Since this will be a SSD raid 0 array, the write amplication is already reduce by 50%, the IRST drivers for ivy-bridge z77 chipset has SSD TRIM support to keep the SSD array in top form.
Since you want top performing games, install a software RAM drive 2-3GB in size to cache all your Windows TEMP/TMP & virtual memory if it's activated. It minimize the use of your SSD array & keep everything in RAM for speed/performance.