I would say, that power supply will last a very long time
System Type: 1 physical CPU
Motherboard: Regular - Desktop
CPU Socket: Socket LGA 2011
CPU: Intel Core i7-3820 3600 MHz Sandy Bridge-E
CPU Utilization (TDP): 90% TDP
RAM: 4 Sticks DDR3 SDRAM
Video Card 1: AMD Radeon HD 7950
ATTENTION: FOR PERSONAL, NON-COMMERCIAL USE ONLY
Regular SATA: 2 HDDs
DRAM SSD: 1 Drive
Flash SSD: 1 Drive
DVD-RW/DVD+RW Drive: 1 Drive
Fans
Regular: 1 Fan 80mm; 1 Fan 92mm; 2 Fans 120mm;
Keyboard and mouse: Yes
System Load: 90 %
Minimum PSU Wattage: 342 Watts
Recommended Wattage: 392 Watts
I also came across a 7950 comparison and they did a power consumption test, worth a look
XFX & Sapphire HD 7950 3GB Review @ OC clubcheers