With my Z68 MSI GD65 board, I have a Marvell *UGH! with two SATA III ports that will take two in Raid O (Remember Raid 0 = two hard drives minimum) and the intel's 6 SATA III ports take the rest in it's own array.
With your system, I am half tempted to just add that disk to your existing array. The more drives, the more horses there are when the data wagon needs pulling or pushing.
With the PCIe x8 Slots effectively destroying (And USB 3.0 too.) the old SATA III interface I am half tempted to simply just keep adding SSD's to existing raid. One array is easier than two. I did "Fly" on two arrays for a while until Marvell's own flaws drove a stake in that idea.
Raid controller Cards for a variety of slots come to mind.
I am assuming ( I know, assuand me...) that some boards only have one SATA controller onboard.
Reaching back further in my mind which is increasing becoming badly in need of defrag and reimaging... I recall that some RAID Bio'ses will allow you to build any number of arrays, "Volumes" you please as long you got the required drives for em.