What are you expecting the GPU to accelerate? The only feature that After Effects uses the the GPU to accelerate the rendering of is the ray-traced 3D renderer, which is an obsolete feature that you'd be better off not using in most cases.
After Effects uses the GPU for almost nothing else.
See this page for details:
See this page for resources about making After Effects work faster: http://adobe.ly/eV2zE7
What the man said - at the moment, there isn't a single feature in AE that would in any way benefit from your cards. Unless of course you do raytrace stuff, that is.
Some third-party effects (Element 3d, Red Giant Universe, etc.) make use of the GPU, but, as the others have said, if you're not using them, the GPU is gonna sit there idle with AE.