P5K Premium issue

[sesdave]

Yup, I know there's not much differences in usual real world applications.
Though, as this computer is also my workstation for professional multimedia works, I planned on using RAID 0 for media applications and treatment, and RAID 1 for sensitive data.

Even then... buying a RAID board which can't work in RAID mode... sounds disappointing

Some suggestions
1-If you want to go RAID in future have you tried changing from AHCI and setting up matrix raid0/1 on your 2 drives now - the different driver might remove the problem
2- If problem still persists you could try connecting to the Jmicron controller
3- If problem still persists and you still want to keep the MB and get the best disk performance you could always invest in a PCI-E RAID card and forget using the ICH9R. It means more spend but at least its forward compatible with any MB. That would give you the overclocking capability of the MB and top disk performance.