I'm building a new video stream/file server for about 150 users, not all of them will be accessing the data at once. I was thinking about getting the Asus 3600 series AM2 motherboard, however I was going to do a mirrored RAID 1 (nesting it's called I believe) with 4 hard drives (2 ea raid) so I think it would be RAID 0+1.

Do most people use the onboard motherboard raid or buy a solid RAID card (and pricey) like Adaptec with a more robust fucntionality?