Sooooo, squeezing the MSI R9 390 into the Core v1 meant cutting away lots of the metal from the case. Literally bled for this build. If you are dead set on this video card it's probably best to find another case, even after cutting much of the left side of the case away the clearances are tiny, less than 1mm for the fans. The fan shroud on the card also pushes the left side of the case out about a half of 1mm.
Proud of my tiny powerhouse!