System Randomly Shutting Down

[njnick3]

Fairly infrequently, my pc will completely shut off. Ordinarily, I'd believe the PSU to be the issue; however, this happens regardless of whether or not my pc is under load.

Specs: http://pcpartpicker.com/p/yb4Vgs

CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor ($219.89 @ OutletPC)
Motherboard: MSI Z87 MPOWER MAX AC ATX LGA1150 Motherboard ($114.99 @ Newegg)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory ($62.99 @ NCIX US)
Storage: Silicon Power S60 120GB 2.5" Solid State Drive ($59.94 @ OutletPC)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($49.98 @ OutletPC)
Video Card: Gigabyte Radeon R9 290 4GB WINDFORCE Video Card ($289.99 @ Newegg)
Power Supply: Rosewill 550W 80+ Bronze Certified Semi-Modular ATX Power Supply ($49.99 @ Amazon)

EDIT: I should mention, this PC is fairly new (1 month, give or take); today, I tried changing the fan curve on my GPU through Afterburner and a few hours after, the first shutdown happened. I promptly uninstalled Afterburner, but the shutdowns have still occurred since. Windows memory test didn't reveal anything.

 

[tiny voices]

Sounds like PSU still. a low quality 550w unit will NOT cut it for an r9 290.

 

[njnick3]

Sounds like PSU still. a low quality 550w unit will NOT cut it for an r9 290.

That's what I would say, if it was only happening under load; however, it only started today and persists even if I'm only browsing the web and using Spotify.

 

[tiny voices]

Can still happen if the PSU is not providing smooth power. I'm still better PSU. It should be replaced with a quality unit regardless.

 

[njnick3]

Can still happen if the PSU is not providing smooth power. I'm still better PSU. It should be replaced with a quality unit regardless.

Ok, thank you