Possible cause for BSOD?

I originally had an EVGA 8800 GTX in the system and I was getting constant BSOD's while gaming. Then I replaced it with a XFX Radeon HD 5570 as a temporary solution, thinking the 8800 GTX was messing up. As a result no more BSOD's :). Now I installed a new XFX Radeon HD 6870 Black Edition everything was going good and BAM! BSOD during a game, and it happened again, usually 20-30 mins in. Now I have a theory, is it possible that the PSU is causing this? I think since both the 8800 GTX and the HD 6870 use two 6 pin connectors the PSU is getting overloaded. And the temporary fix HD 5570 doesn't require separate power, so maybe that's why it works fine. I have a apevia 600 watt PSU and it works fine with the HD 5570 and it was working right for almost 4 years with the 8800 GTX. Any thoughts?

Attachment 127599

Dumps blame atikmdag.sys, your ATI display drivers

- Boot into safe mode with networking
- Uninstall the ATI drivers including Catalyst Control Center
- Use driver sweeper to remove leftover ATI display driver files Guru3D - Driver Sweeper
- Install the latest drivers ATI Radeon
- Reboot into normal mode

Test your RAM RAM - Test with Memtest86+

This error is caused by bad RAM/GPU, insufficient PSU, defective PCI slots or a corrupt driver

Code:

BugCheck 1000007E, {ffffffffc0000005, fffff88004bdbc6d, fffff880029bfc88, fffff880029bf4f0}

Probably caused by : atikmdag.sys ( atikmdag+3c5c6d )

i'm pretty sure its not a driver issue. when i had the 8800 gtx in there it blamed the nvidia driver. I've also done mem test with quite a few passes with no issues. I bought a 750 watt psu today and i just installed it. I'm gonna test it out tomorrow after work, if i can game longer than 2 hours i should be in the clear.

I'll let you guys know the outcome.