I would see if there is any settings in BIOS to wait for each HDDs to spin up and POST. Also although you have a 1300W PSU, if 10 drives spin up at the same time, the overall current may still exceed limit. Does your backplane support spinning up the drives one by one?
The main problem I have is the arrays disappearing after the OS has booted and has been running for a while. I don't typically have an issue with the arrays immediately after a reboot although I have seen this at least once. I will have to check to see if the backplane supports spinning up the drives one by one and I will also check the BIOS settings tomorrow as you suggested.