Ok, take pc out of the cubby and see what happens to the temps.Not exactly zero fresh air. The front of the cubby is completely open, where the dual 120mm intake fans are. And there's a few inches at the top, between the top of the PC case, and the upper shelf/top of cubby. The problem is, the back of the cubby, only has some smaller openings at the bottom and top rear, mostly for cable routing, and not airflow.
This is compounded by the fact that the case has no top ventilation.