That's not possible. Such stuff requires two cards with the same capabilities, essentially meaning identical cards and their CUDA usage is controlled by the driver and their SLI settings.
And, on top of what Mylenium said, AE doesn't use the GPU for much.
The (obsolete) ray-traced renderers is pretty much all AE used it for. Now, some third-party plugins do use the GPU, but their requirements and usage have nothing to do with whether AE "recognizes" a card or not.
Official word here: GPU (CUDA, OpenGL) features in After Effects CS6 and After Effects CC