Try shopping on a site with a good return policy, and try the DIMMs. Chances are that the mobo will just underclock the DIMM to 1333MHz, and it won't matter.
Use the SATA 3 (6Gbps) ports, you might be able to get about the performance of the raid from 1 drive.
I'm not sure about if you can do raid on the marvell controller, though.
When I wake my computer, the screen is completely black. I can unplug, and plug back in one of the displays, and it will work again. This happens on another computer of mine, too, ruling out hardware weirdness.
Both computers are running Windows 8 Pro x64, and have an AMD Radeon HD 6870, and...