I think the CPU would need a good way to exhaust in a vertical layout, not to leak heat into the intake of the GPU, but it looks good for horizontal. I really like what you did for the mains power cable, and where it ended up haha. Maybe instead of having to do an angled cut for those cable passthroughs, you could make a cut from the top, and just lay your cables over the wall, or through a wall gap. Maybe the wall could be a separate part, attached using fasteners to fix them together. That would turn this into 3 parts instead of 2. You could also make it a flat piece then, in the place where it meets the front face, just with the GPU cutout parts. It could include the cutouts for the GPU IO plate too that way.
Im getting too enthusiastic about this case at this point, I'm excited to see what happens in the end regardless. It already looks very interesting.