R4 and 780> powersupply compatability?

I have been looking to see what my R4 powersupply is rated at, but not finding anything. 

I am upbrading 2x 680's to a single 780 and am having problems that all seem that the machine it not supplying the needed power..

Any input would be greatly appreciated.. Unit is 1+year old but kept in top condition, just need to get this darn 780 to work.

Thanks