My $0.02:
If you don't have time for regular backups, you are gonna end up getting ****ed no matter whether you go with RAID IDE or SCSI or straight drives. If it's important then back it up!
I wouldn't even consider a 10k scsi drive; I'd get the Raptor SATA 10k no question. Performance is similar while you skip the cost of a scsi controller. I have a single newish fujitsu 10k and it is no huge performance boost over my 8meg cache WD 120gb drive. If you are going to use SCSI then quit ****ing around and get a 15k rpm drive. Then in a week when that's full then grab a 200gb ATA drive for pr0n storage