Not exactly a standard choice of psu. I've not seen a testing review of that model, but coolermaster are rarely recommended on here. Regardless of its age, failing to post is likely to be the psu. Do you have a spare you could test with? If not, remove the gfx cards and see if it'll post. Under far lower load it's more likely to boot even if the psu is dying.
If the motherboard is dead diagnostics will be tricky. Try booting with one stick of ram, one graphics card, processor, no hard drives. You're hoping for a normal post sequence which ends by complaining that it cant find any boot media.
Next try booting with processor, motherboard and nothing else. You're hoping for beeps complaining that there is no ram, if it fails to beep it suggests the motherboard.
Be aware that if your psu has died, it may have died gracelessly, harming other components.
