It's not really worth testing, it doesn't even support GPU'shttp://www.hwtools.net/Adapter/PE4H.html
The only other option is the GUSII, and it only supplies like 75W of power. You might get a 750 Ti on there, but it won't run fast enough.
That defeats the whole purpose of having a dedicated GPU.
I'd test with an old PCIe card and see if it even works before buying a $1200 card that will be bottlenecked on your processor and PCie 1x speeds.