Cheap psu's are not reliable at all, they are made with cheap chinise capacitors and when given a bit of load they get short circuited, and then either your rig will be burned or your house
So, its always good to buy a effecient and branded psu so as to protect your expensive rig
As Linkin suggested you could buy a XFX 650 W 80+ Bronze certified psu
Tell me where do you live and i could suggest something else
P.S dont forget to click on Pick as solution