Wrong. Gold is not very good at heat transfer. In computer components use anyway. Gold might cause whatever you are cooling (processor, GPU, etc.) to break due to weight and cease to function. Aluminum is even better than gold, not in sheer transfer, but in cost andheat dissapation, and yes dissapation is different from transfer. Both copper and silver are better than gold, but copper is not the best. And dear God, what the fuck are you smoking thinking that plastic is a good conductor of heat. Just because something melts doesn't mean it can transfer heat well. The atomic bonds are just weaker than in more solid elements and compounds. to answer the topic...
Silver is the best available material to make a heatsink. It is the best metal* available to transfer heat. Yes, even better than copper, but much more expensive.
*Diamond is the best thing, PERIOD, for heat transfer. It is just impratical and too difficult to shape properly.