Thanks for your response.

All three supplies are single rail ones with 840w, 744w and 360w max on 12v rail.

I added 150w for cpu etc., I'm guessing youre saying 100w would be enough? It probably would since the cpu is 65w tdp.

Other than that my calculations are the same as what youre saying. So i guess we're thinking I might be able to pull it off without cutting the risers.