RAID10 and RAID0+1 (and RAID1) have the same level of economy (namely, not much). RAID0 would be the most economical, except that it's not really RAID, as it provides no redundancy. After that, it would be RAID3/4/5, all of which have the same capabilities for economy. It might even be slightly preferable to use RAID3 over RAID5 for an mp3 collection, but the benefits would be marginal, if existant at all, and it's hard to find RAID3 implementations these days, anyway. But, again, RAID5 is slow (as are RAIDs 3 and 4), but mostly for writing.