Raid for imac / imac or mbp

Hi.

I have an Imac with firewire 800 and looking at purchasing an external RAID 0 box with firewire 800 for video editing. I have been looking at specs and most have said speeds max out for firewire 800 at around 100MB/s. Right now i have an external WD Black drive that reads/writes at about 60+ MB/s with benchmark tests. Just wondering if the speed increase would be noticable since i am limited to firewire 800 and the WD black drive is fairly fast. I would have thought I would get more than 30-40MB/s faster access time with a RAID with 2 drives than 1 drive, but they did say the black drives are a lot faster.

I will be upgrading to a mac pro eventually but the speed of the imac is ok for me at the moment, however I have thought about side grading to a mac book pro of the same speed so i have atleast an express slot for upgrading. Just wondering if this would be worth the consideration as well, or would the express slot for either an esata controller or video render card be worth it.

As much as i like the imac i wish and think it should have the same upgradability options of the higher end mac book pros.

Thanks
Mark