Ducting CPU or GPU???

I would like to now if I should duct the CPU or GPU, I'm planning on buying a Tt Tsunami case and will use the 9cm fan mount of the side for the duct.

CPU will be: AMD Athlon 3500+ (socket 939)
GPU will be: ATi X800 (PCI-Express - I hope, if not X800XT)

Any help would be greatly appreciated, thanks.