So an obvious question: why would you put a hot card like a GTX 690 into a case where it "exhales" straight into a solid plexiglass window? That seems far less than optimal. A better design would've had the video card facing up, and with all that space in that (relatively speaking) huge enclosure, would have offered some airspace to vent into.
My little Silverstone case has an immense quantity of room surrounding the PEG slots; the space and the cooling flow is perfect for hot PEG cards to ventilate up and forward, drawing cool air in from the front and out the well-perforated back along with a draw-through fan at the top. I understand that my case isn't likely to meet your aesthetic wishes though