I don't think it's power related... I've got mobo and 2 cards on a 750W Gold and the other 3 on a 1000W Gold. I've looked at the logs, Alexis is the miner that crashes in 90% of cases. Tribus crashed twice too. Disabling them altogether and testing now again for 24 hours.

On a sidenote, the Spmod miner uses powershell... But that closes straight away for some reason and doesn't work at all. Very weird.