Please help with system upgrades! ?

Zdux19

Honorable
Aug 31, 2013
13
0
10,510
Hello all,
My current build is as follows:
Intel i5 3570k overclocked to 4.4 ghz
Asus p8z77-v lx mobo
Xigmatek dark knight ii night hawk edition cpu cooler
8gb corsair vengeance ddr3 1600 ram
Wd 1tb caviar black hdd
120gb kingston hyper x 3k ssd
Evga gtx 560ti oc gpu
Ocz zt series 750w psu
Lg optical drive
Cooler master haf x case with 4 200mm fans and a 140mm rear fan

Not sure what to go for first as most of my hardware is somewhat outdated. Also my computer freezes every so often so that you can not move the mouse and you have to hard restart it to get it working. I was wondering if the psu could be to blame as I heard that it is not a very good one. This also freezes with the cpu on stock settings and I stress tested for 24 hours with no errors after the oc. Any help with these issues would be greatly appreciated. Thanks in advance.