Are you sure?
According to my UPS the system is never consuming more than 150W
The 115VAC power consumption is not the same as the power consumption on the +12VDC, +5 VDC, and +3.3VDC outputs (as well as others) which is how a computer power supply is actually rated.
I also agree that you are likely pushing your power supply to it's limits. The only way to know for certain is to measure each load or find out what the maximum power draw is for each load. But even then, as a power supply is pushed harder typically there will be power fluctuations (un-clean voltage). Now I'm not saying this is your issue here but as some friendly advice, I would recommend you re-evaluate it.
don't think that the Sata-Cables are faulty because this morning I had errors on da1 and da5 and on other days da2 and da4 had errors as well, it's totally random and very unlikely that 6 Sata-Cables are wrong seated, no?
Yes, it is possible for it to be the cable. Let me ask you this... Are the drives all connected using one SFF-8087 cable? If yes then relocate the cable to the other port and see if that works. If you have the drives split across two of these cables then are the affected drives on a single cable? The common denominators here are: 1) The SFF-8087 Cable, 2) The M1015 Controller, 3) The Drives. Odds are, and we have seen this before more than once, the connections were disturbed and need to be remated or the cable actually went bad. Also, what is the length of the SFF-8087 cable? If it's really long, you migth try a shorter cable.
Regarding the power consumption I just trusted the numbers on Amazon. But it's still about 50% more Power Consumption on Load in the Spec Sheets you posted.
[xtable]
{tbody}
{tr}
{td} {/td}
{td}WD Red {/td}
{td} Seagate {/td}
{/tr}
{tr}
{td}Start Current {/td}
{td} 1.75A{/td}
{td} 1.8A{/td}
{/tr}
{tr}
{td}Ave. Current {/td}
{td} 4.5W{/td}
{td} 6.8W{/td}
{/tr}
{tr}
{td}Idle Current{/td}
{td} 3.3W{/td}
{td} 4.4W{/td}
{/tr}
{/tbody}
[/xtable]
I can see that you were looking at the average current draw which while it is pulling ~50% more power, it's not a major consern. I was looking at the startup current which is ~ 21 Watts (Amps x Volts) per drive and this the factor you were really pointing to when you originally stated that your PSU could be the problem becasue the drives were pulling 50% more power. They pull a combined total of ~1 Amp more power while they are operating and that is insignificant in my opinion. So while I don't think your PSU is at fault here, if you find out it is, the fact that it failed due to replacing the hard drives would mean that you were really pushing your PSU for a while and I don't believe that at this time.
Okay, getting back to the problem at hand, check your cable(s) and you might need to replace it.