I'm going to do something similar to this soon. I'm going to have a cool air intake which will consist of 2 120mm PC fans, and some PVC pipe. The fan outside will suck the air into the pipe, while the fan inside on the end will blow that air in. Then I'm going to cut a hole on the top-right of my shelf and install a pvc pipe with 2 120mm fans as well. It will suck the air into the pipe, and shoot it out.