It is nice to allready have one included with the Video card itself.
This 37 degrees C. is Idleing here browsing the web but I've never seen it over 57 C. during SH3 or a frame puller like FarCry.
But this Nvidia GeForce FX 5950 Ultra 256 MB AGP card ( 2 years old now I think ) has its own two fans plus there are 8 more fans in the computer keeping things cool as "Alienware" designed it.
My computer room is allways around 72 F. and I've never had a computer heating problem. ( Knock on wood
)
Knowing the temp of your GPU is a good thing.