All hard disk drive brands, speed and capacities can be used in raid environments, but generally you would want the same brand and should favor the enterprise models as they carry longer warranties and generally for not much more in cost. For storing music, it's fine to go for the slower drives, and will save power as well. If you had a true hardware raid card costing $500 or more, then you might be concerned about the drive features. For software raid which is a safe bet on what you have or would get even in those dedicated raid enclosures, it's not going to matter.
Personally I wouldn't consider a RAID with all the cheap solutions for online backups. Just one or more large drives for the tunes, online backups, and then you can go the extra mile and still do local backups. You can do all of that cheaper than a basic raid5 setup and I would argue much more sound backup solution. The only next step is to backup the original cd.
Keep in mind that a raid solution isn't a backup, just a way to increase reliability and minimize down time. Its a great solution for extremely large libraries but as drive capacities increase they just become expensive.
Also I think an online backup solution is cheaper and easier.