Strange Issue - Urgent Help Needed!!

Hi first off not sure if this belongs here or in BSOD so please move if more appropriate there. Just built a new PC and it cuts off to black and reboots occasionally. Temps seem fine, yesterday I did a memtest with 4 passes 0 errors. Also updated all drivers. The guys over at r/techsupport suggested it was PSU so I decided to log as much HW info I could with HWiNFO. One of the games where this happens is while playing Assassin's Creed 4.

Antec nine hundred case
Raidmax 835w
nVidia gtx 770
4670k not oc
1 wd hdd 7200 rpm
1 ssd
Asus Z87a mobo
2x4gb 1600 ram
Hyper 212 cpu cooler
1 optical drive

If I missed some parts or you need more info let me know.

I thought the psu is fine but :/

I would suggest power supply brands like Corsair, Seasonic, XFX, they are really good. It sounds like a psu issue to me.
Borrow a known to be good psu from friend/family member and see if problem continues. If the problem goes away, get a new power supply. :)

As said above try and use a different psu for testing. Raidmax has little to no user feedback online. At it's price point I would not expect a lot. When choosing a psu one name and one name only, Seasonic. There are other good psu's brand names, probably made by Seasonic. Seriously, a 850 watt psu is going to run about $150+ for a quality unit.