Here's an idea of the measurements and clearance that you have with the extended PSU shroud.
There's a goodly bit of space here if someone wants to get creative and use it as a canvas. I'd really love to see what folks who are less "graphically challenged" than I am could do here.
Of note is the 55mm of clearance that you have from the front of the shroud to the back of the fan mounts. That should be just enough to mount a radiator in push/pull configuration.