Need advice with 4x 290x and 990fxa-UD5

[Commodore]

1250W PSU is nowhere big enough, 4x 290X can easily draw 1200W by themselves.

My problem now is fit in 3x 290x tri-x , as i wrote before stock air cooling system is bigger(3mm wider then 2U slot) than i can insert without risers in 1-3-5 pci-e slots. I hope 1250w would enough for 3 cards when i modify stock cooling or buy another cooling, don't want to go for risers yet.