as long as you drop the video card

As I wrote below, some motherboards won't POST without a GPU.

Take only that extra and you probably have a few years usage before additional electricty costs overrun NAS cost. Where I live that’s around 5 years for an estimated extra 10W.

Yeah, and what's more, if one of those appliance-like NASes breaks down, how do you fix it? With a normal PC you just swap out the defective part.