I have a Coolermaster real 850W (I don't have the model here). Total system consists of a i7 975, 6GB memory, 3x320GB HDD in Raid 0 + 40GB SSD, 1x Quadro FX1700, Gigabyte MB X58A-UD7.
That psu is more than enough so you are well in the clear. Since both cards are DX10 SM4.0 they are unlikely to have any issue but I can't rule out any other issue except power. Good luck.