I'm not sure your PSU draws enough power to plug more than 2 graphic cards on it
What do you think ? Are you trying to plug 3*GPU to a 600W PSU ?
PSU has nothing to do with it since his cards aren't even properly recognized. No graphics card in idle consumes more than 25-30W, most consume a lot less, so power doesn't matter at this point. It only becomes important when you apply the mining load, but not at the initialization stages. What do you think ? Are you trying to plug 3*GPU to a 600W PSU ?
One last thing that I thought of before really calling it quits. I have one of those PCI-E splitters. Is there any reason to believe that if I unplugged 2 of the GPUs from the mobo pcie slots, plugged the splitter in and plugged those 2 GPUs into that it would work? It might seem far fetched but I'm trying to exhaust all avenues to get this thing to run with my 4 GPUs.
If you already have a splitter, then why not try it? 
Shouldn't take more than a few minutes.