Personally I would suggest going down the road of RAID 5 - it will be a bit more expensive to set up than RAID 0, but with RAID 5 if one drive fails then your data is still OK. In a RAID 0 array, one drive dies and all your data is gone - and the chance of one drive failing increases when you use more drives.
+1
Definately go RAID 5 or 6, RAID0 multiplies the chance of you losing all your data by the number of drives in the array, so a six drive RAID0 array is six times more likely to fail than a single hard drive losing everything.
Only consider proper hardware RAID cards from people like LSI/ 3WARE Adaptec etc, software based RAID is no good for this sort of application, you want something that does all its own processing.
Also data rate wise a single stream of 4:2:2 1080p HD footage works out at about 7.4Gb per running minute so a sustained data rate of 123.33 Mb second. Thats not actually too bad!
You may still have to look at SAS drives rather than sata though, as from my experience using standard sata drives in a large array doesn't give great performance. We have some big file servers that are used for archiving work that run 8 x 750Gb and 8 x 1Tb Sata drives in RAID5 (two different arrays) on an AMCC/3WARE sata controller and yet barely acheive 150Mb sec sustained data rate.
If you're going to be working at your new devices full 4:2:2 at 1080p and want to run multiple streams for editing/ compositing etc, I'd be suggesting an 8 drive array on SAS drives running RAID5. Not gonna be cheap though!
E-I