Only option to cool down your room is to vent your computer exhaust out a window. A dryer duct or an outdoor radiator would work. Any type of water cooling or after market heatsinks will just heat your room more efficiently.
You didn't read the thread.Although I have never even looked into WC'ing, I think that is your best option. You are pretty much guaranteed reduced heat output with WC'ing it.
OP, you can see if your video card is underclocking when idle using a tool called GPU-Z. You can get it here. What does it say for GPU and memory clock and voltage at idle?Does the 4870 underclock itself in 2D mode? Some of the NVIDIA cards do this, which will drastically reduce the heat output (and power usage) while surfing the web etc.
How small is your room? Surely a GFX card on its own can't put much heat into a room? My computer room is always warmer than the rest of the house but thats got my main rig, server and a Pioneer AMP & separates. The AMP takes over 530 watts of electric and puts out a LOT more heat than both my PC's put together.