A system with a R9 290X is recommended to have 650W with 33A on the +12v rail and two PCI-e connectors
The GS700 comes with 700W and 58A on the +12v rail and two PCI-e connectors.
It is a tier 2 class A PSU on tom's tiered power supply list Tier two class A - Excellent quality units, if not, as good as the Tier one class of units. For people who have a limited budget, but still want a reliable unit for the price
To answer the question, it is more tha enough in fact a 650W is perfect. But if you plan to Crossfire the 290 then to future proof it get a 800W-850W PSU.
A system with a R9 290X is recommended to have 650W with 33A on the +12v rail and two PCI-e connectors
The GS700 comes with 700W and 58A on the +12v rail and two PCI-e connectors.
It is a tier 2 class A PSU on tom's tiered power supply list Tier two class A - Excellent quality units, if not, as good as the Tier one class of units. For people who have a limited budget, but still want a reliable unit for the price