I have two port pci-e card with only one ssd in it at the moment most definitely an improvement over the SATAII of the system bus and don't get too hung up on the 3.33 there is a 3.2 model I have seen going most time hundreds of dollars less than the 3.33 your never going to notice that 1 or 2% difference.
Thats true. What is the exact model number for 3.2 hex for my MP?
Anyway I'm still doing SD video and 720P,1080P at most so for me,having internal soft RAID0 with two regular HDDs is fine. But I'm pretty sure throughput of the drives will be major bottleneck before CPU. If I were doing majority of stuff in 1080p and above, I would have long gone with external solution. eSATA enclosures are priced very reasonably from my experience,you can stack up ´ole regular HDDs for max capacity (at 4k you'll need it) and stripe them for speed. Reuse your FW800 drives for backing up this RAID because speed isnt really important for backing up mostly.