Have you tried closing in the top so the front fan air flow is kept within the frame and exhausted out the rear? Also, how about reducing the airflow above the heat sinks (reducing the upper front fan opening) so as to improve cooling efficiency (greater air flow through the internal heat sinks)?
Beyond that, how about an S3 fan both on front (push) and rear (pull)?
None of these seemed to make any significant difference. The loudness and temperature seems almost entirely dependent on the one fan on the front.