Ok, I decided to do a test using one chassis fan (until I find a solution). Everything appears to be spinning but I don't have any visuals or sounds. My new benq screen is plugged into the motherboard (on the back of the case) but doesn't detect a signal. Might this be because the screen has to be plugged to the video card or not? I don't have an HDMI cable so I can only use the plug on the motherboard.
Also, about the video card. I got two plugs in it (6 pin and 8 pin I think) and those two cables then each split into two molex adaptors which I then connected to the power supply (4 times). Is that right or do I need to connect it with something else?
Coudn't find the Asrock board so that's a pity. But I think the ASUS isn't that bad either.
Everything seems to be whirring though (the one chassis fan, cpu fan, video card, green light on the mobo) so I think its just the visuals who aren't working. Not sure if I'm supposed to get a sound at this stage.