Problematic update nvidia gpu pci exp 1x16 v1?

Question

NVIDIA

It's easier for me to buy an additional
power supply than a new mother and a new cpu and a new vidyuha .. and a new operative.

I just love big monitors and 4k movies,
well, I love the perspective
like dx12 + fresh shaders + 3 monitors at once,
well, even when I change mother to pair a pair of nvidia gpu. ..

power limitations? 150 watts per vidyuhu - pci exp 1x16 v1 (vidyuha 970 maximum)

but if add bp then with external power supply and good cooling there is no limit on power supply of 150 watts
but the bus speed will remain only a limit? (is it critical for 4k movies?)
stone = core2duo 2.2 e4500...