I agree. You are pushing it with that close to the limit of the PSU. IIRC, I use a 700 watt PSU with roughly similar load required. I've seen a review of no brand PSUs that fail immediately at that kind of load compared to their rated load. When you see me rolling my eyes at excess PSUs, that's been people recommending 900 watt units for normal PCs.
Edit: Actually 600 watt PSU with 400 watt recommended
Edit: Actually 600 watt PSU with 400 watt recommended