Your mobo does not require DRAM with AMP settings programmed into the SPD to run at 1866 MHz. Asus mobos IME are very DRAM sensitive and often DRAM listed on the Asus tested and approved DRAM list does not always function without issue. Many PC users have experienced a lot of headaches with DRAM on Asus mobos compared to other brands of mobos.
Any DDR3 RAM that is rated at 1866 MHz. (as a kit, not as individual DIMMs), should run fine on your AM3+ mobo with the FX-9590 if you manually set the DRAM timings in BIOS to the specifications provided with the DRAM kit. When you buy DRAM with AMP settings these are read by the BIOS when you boot up and the BIOS tries to set the AMP timings and frequency - just as you can do manually if you understand how to do this. Not many companies sell DRAM with AMP settings so you may desire to try manually setting the G.Skill DRAM if it is rated for 1866 MHz. The proper timings for the G.Skill to run at 1866 MHz. ( if it's rated for 1866 MHz.), should be on a label on the DIMMs or on the package the DRAM came in.