I've got a similar setup with the cpu and gpu. I have a 550W Gold power supply. You are definitely fine. I actually looked at Rivatuner stats to see the power consumption and even in very intense, real life scenarios the whole setup draws 250W at most (direct software reporting, not from the wall, but it seems smack dab in the middle of the efficiency curve of the power supply, so I'd expect a 300w or so draw from the wall - and for you even less as you've got a Platinum rated PSU).