Frequent BSOD and freezing

Can you list the GPUs you're using. Primary first, then list the alternate ones you have tested. When the BSOD happens, does it go straight to BSOD Dump screen or does it hang and make a loud annoying sound with no video (this is providing your sound to monitor/rack is going through HDMI.)?

If your GPU drivers are crashing, try a clean intall of the drivers using the current stable/recommended drivers. Uninstall current drivers, restart, run driver sweeper (select only NVIDIA/ATI graphics drivers), restart, re-install new drivers, restart and then see if that works.

Also, monitor your GPU temps. I ran into the problem with my Zotac 570. Needless to say, I will not be purchasing anything from them anymore due to the fact that their CS is aweful and the fans failed within 2 days of installing the card.

Beware of any 3rd party GPU overclocking programs if you dont know what you're doing. Download MSI Afterburner but dont touch the sliders for your shader and clock speeds. Use the on screen display addon to monitor fan speeds, temps, usage etc.

Since you already re-installed windows, I doubt that is it. Try to replicate the issue to the best of your ability. If the GPU drivers do not work, it could be RAM. Pull out all sticks but one, replicate, add until failure. You might have one that is bad.

I also recommend downloading Blue Screen Viewer.

I hope this helps, at the very least it will get you started until someone more skilled in these issues posts.