You have done great job trying to solve this issue. So, right now, when you press the power button you hear some typical noises, but no signal on screen, right? You have tested big part of the hardware, so I would recommend you to try booting with only the PSU, the processor and a slot of RAM connected. If you still cannot get any signal, you may be facing a power supply issue. Sometimes the provided power is enough to run the PC. Please check that.
Hope this helps