If I could get multiple disks, I would still go for single junctioned installs... here is my reasoning.

say I had 5 disks, I would have:
1x Disk - OS
4x Disks - stripe (RAID0)
I would backup essential data off the stripe onto the system disk.

This would give the benefits of interleaved access from 4 drives and the benefits of the cached data as it would be retrieved from the same physical disk.