Greetings Nick,
You have 4 disks, 2 SSD and 2 barracudas. If you exchange one of the SSD's that only leaves the barracudas for RAID. Or am I missing something? You don't want to mix RAID across SATAII or SATAIII interfaces. Could you, yes, but you'd be doing yourself a disservice.
If you purchase a 3rd SSD (256GB) and don't plan to put your OS on a RAID, it needs to be put on SATA3 ports 0 or 1.
In your case, I would keep my OS and CS6 scratch disks on the intel controller. If OS for RAID SATA3 0&1. Put your scratch disk on a intel SATAII connector along with your DVD.
I don't see any reason why you couldn't or shouldn't move your barracudas to the marvell controller as single disks or as a RAID. If you want speed, create RAID 0, if you want redundancy RAID1. While the marvells performance is not astounding, it works perfectly well as an alternative and balances things out when performing large data transfers, etc. Let me know if had something specific in mind I haven't discussed.