Ati Radeon 5750

kind of weird, that card uses very low power I don't see why it shouldn't run.

yeah that's what I want to know too...

When I connect the PCI-E and attempt to power on, I don't even hear any signs of life.. like any slight hint of the PC wanting to turn on, I only see the light on my power button go on however..
I've faced this same exact issue with my 480W PSU but that one was weaker on the 12V lines.

Also note that I transferred this PSU and GPU to another motherboard(PC) and attempted it.. nothing happened, same exact problem. PCI-E connected . = No signs of life , PCI-E disconnected = System boots . Fans all turn on and it even beeps too just as it does in any regular startups.

Rma the card!

So my PSU is good right?  
Just want to make sure

have you tried 'PEG' (pci express graphics) or something like that (means switch to dgpu before pluging in power cables in gfx card) as your primary graphics adapter in bios.

I've heard of that but I don't think that's the cause of my PC not being able to power on? I've heard of people who's issue might be that but their PC powers on, only to find out that they don't have any display.
I however can't even test it out to see if I even receive display as I am unable to power my PC on with the PCI-E connected to the card.

Man you say you got a 480w psu. But you did not tell what brand it is . Telling its brand will be helpful. And the antec 400w psu is more than enough for your gpu.