How much PSU wattage will I need?

dashboy1998

Honorable
Feb 4, 2013
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I am thinking about getting a 2nd GPU.

CPU: Intel i5 4570 @3.2Ghz
RAM: DDR3 4GB x 4
Mobo: MSI B85-G41 PC Mate
HDD: WD Blue 1TB
SSD: OCZ VTR1-25SAT3-128G
ASUS 24X DVD Burner

PSU: OCZ ModXStream Pro 700W

GPU: MSI R7950 TWIN FROZR 3GD5/OC

I have one gpu now and its not OCed