I'm not sure if it is possible but check and see if you can fit one or two smaller fans in the front of the A3000 I guess about where the CPU slot sitts (and even seal other parts of the case from air leakage with dukttape). Just to get better airflow, cooler air where it's needed and to prevent junk from being drawn in trough the diskdrive(s).
I sold my A3000 machines quite some time ago so don't remember how much room there was left in the front.
