I bet it is a FSP sourced PSU like the Silverstone ST45SF (80Plus Bronze) or the BeQuiet! 450W bronze one ;)
edit: it definetly is the same FSP housing ;)
edit2: 2015 seems to be the year SFX PSUs finally take off, with Silverstone, BeQuiet, Corsair, Fractal, Dirac, and many more in the ship.
BeQuiet DarkRock Top Flow
it might just perfectly fit on the Asus Impact Z87 in the M1.
... or maybe not ?!
edit: it might interfere with the top panel, though there is some space between the border of the motherboard and the top panel.
also the cooler might fit turned 180ºC
who says, that the Asus is either the "quietest" or coolest?
afaik the sapphire vapor x version of the R290x fits.
edit: wait you want two use three (3) 3.5" drives ???? than only dual slot cards can be used.
Do you still have a huge collection of VHS cassettes?
Things get obsolet. If you can't live with the fact that a case doesn't have a optical drive, then that case just might not be it for you. By what argument would you force all other users to live with a (for them) useless hole in the case...