Are you plugged in to the black SATA ports? If you have SATA port 4/5 set to IDE or RAID make sure you are not plugged in to those. Did you do a fresh install after changing the BIOS to AHCI?
I would also suggest you enable RAID5 support even if you don't use it, I needed to do it to get full performance from my SSD's even though I don't use it.
BTW, I have the same MB and I know it inside and out
The MONSTER HTPC:
CPU: AMD FX-8350.||.Cooler: Corsair H80i
MB: Gigabyte 990FXA-UD7.||.RAM: 8 GB Mushkin Blackline DDR3 2000MHz (7-10-8-27-1T)
Case: CoolerMaster HAF 932.||.PSU: Corsair HX750
GPU:Asus R9 270X DirectCU II TOP.||.Audio: Creative X-Fi Titanium Fatal1ty Pro w/ Logitech Z-5300e (5.1, 280W-RMS)
System Drive: 2xSamsung 840 Pro 128GB RAID0.||.Working Drive: 2xMushkin Chronos 60GB RAID0