Hi guys, just wanted to report that today I've successfully started the rig - with one GPU currently.
It seems that the main PSU, motherboard and CPU are fully funcional and were not damaged in any way. I then used the GPU for gaming and didn't notice any artefacts so it's ready to be sold :) After I clean it...
So for the next days I will be testing the GPUs and putting them on actions. It's not the best moment though as ETH price is crashing and many miners will probably sell their GPUs as well. I hope that it's gonna be mainly AMD Radeons so the GF1080 will keep it's price.