3 SSDs, 2 RAID 0 Which Controller?

I currently have 2 SSDs hooked up to my Asrock P67. One is a Crucial M4 128GB that houses Windows 7, the other is a Corsair Force 3 120GB that I use for my games. My mobo has 4 SATAIII ports, two of which are Marvell SE9120. As of right now the Marvell controller is disabled and my SSDs are hooked up to the Intel controller and set to AHCI.

I'm considering adding a second Corsair Force 3 to run in RAID 0. I'm primarily considering this because the prices have dropped significantly and I'd like to have the extra storage for games. Loading times are significantly faster, but the small space and Steam's inability to install to more than one location means that I'm frequently moving files around between the Force 3 and my HDD.

My primary goal isn't speed, but since I would have the ability to do so I would like to take advantage of running the drives in RAID 0. However, it's my understanding that having two drives in RAID 0 on the Marvel controller would be a waste of potential. Am I correct in my assumption? Would moving the single M4 to the Marvell controller result in a significant drop in speed in Windows?

Thank you.