PC Wont boot with GPU pls help

[Inspirational]

Oh no... 
So this is my build:
https://pcpartpicker.com/list/4DjDZf

I recently formmated my PC and bought a new 2TB HDD and 500GB SSD. My PC was running fine, but after I installed the new HDD & SSD (where I had to take out the GPU and reinstall it) and after rearranging the SATA3 cables for all the drives, the PC lost its connection to my monitors. I uninstalled the new drives (and GPU so I could reach the SATA ports - then reinstalled it) but it didnt help. So I removed the GPU again and changed the HDMI cable from the GPU port to the MOBO port and it had connection again. 

I checked the power requirements, which is apparently around 460, but my PSU offers 650 so it couldnt have been due to power either.

I spoke to my friend about this and he said that it would be risky to reboot with the GPU incase it was fried (and would damage other parts). What can I do in this situation? I've had the GPU for about 2 years and it has never given me a problem before, so I doubt that it was damaged, especially because it suddenly happened and I am afraid to test it in case it really does damage the other parts.

Could this all have something to do with the installation of the new drives? I honestly don't know what is going on and I'm in panic. I can't sink another $700 for a new GPU
Please if you have any troubleshooting methods or ways of getting the PC to boot with the GPU let me know

 

[Inspirational]

Could this be caused by dust landing on the GPU's ports or gold plates?

Could it be MOBO problem?

 

Or a SATA cable problem? Why do I ask this? Because re-arranging them sometimes stops the monitors from connecting. Wtf is going on