you're going to get crackles when accessing too many samples at the same time, especially when you have fast runs. That's because the CPU can't keep upi can't provide the proof right here and now, but i'd say the harddrives and the *road to the CPU* is the problem (file access needs hight priority kernel time, if data feed is too slow, too much CPU is blocked to do anything else).
everything between the CPU and the drive increases overhead, so to have samples on sATA disks connected to an ICH (integrated controller hub, eg. version 7) would reduce this load to a minimum - therefore firewire disks are the second-best choice only.
too bad the mac-minis don't have their 2nd sATA port (from the chipset) accessible from outside ...
christian
and remember: only a CRAY can run an endless loop in just three seconds.