I've put a heat sink from a nVidia TNT2 on the permedia2 chip and installed a large (7200 rpm) fan in the A1200 directly above the gfx chip.
I also have a 15watt heat sink on the 040.
The system has run perfectly stable for several hours (I've not had time to run it longer) but it does sound like an industrial vacuum... my sound meter rates it at 83dB...