I just put together a server/HTPC with a Node 304 case and had some difficulty with fitting my PSU
. Now this is only a 300W unit and would probably not suit your build anyway, but because of it's much smaller form factor (TFX), and different screw pattern on the back, it would not mount to the case in any traditional sense. I had to get creative with some miscellaneous parts around the house, in order to keep it in place.
The two ATX PSUs I had laying around went in fine, although they ate up a lot of space. And there's space for non-modular cables on whichever PSU you buy, I had no difficulty fitting an Ultra X-finity 600W
and its cables inside the case with the motherboard installed. The biggest reason I avoided using this particular PSU was its age, as well a having 2 x 80mm fans on the front/back. I highly recommend that you make use of the massive vent in the bottom of the Node 304 by using a power supply that has a large fan on the top or bottom (which I believe has become the norm anyway).
Best of luck.