If you really want to RAID 1 together two drives, I'd suggest using FW800 to do it. Going over USB is going to limit your speeds, as has been mentioned. Otherwise, using CarbonCopyCloner is great. Scheduled backups/clones and the program doesn't have to be running for the schedule to happen. Much better solution that RAID 1 over USB/FW.
Also, not all RAID enclosures are loud. I have a NewerTechnology Guardian MAXimus, and it's reasonably quiet. If nothing is going on, I can hear it, but my keyboard is louder than it is. Playing some quiet music is enough to get to the point where I can't hear it.