I want to learn how to use AMD Stream and NVIDIA CUDA (PhysX) to calculate things such as locations. I have not yet found where to get the SDK for these (I can't test the CUDA things because I have a AMD graphics card but it's plenty of power for advanced game dev). So do any of you people know where to get these? Or even better a single library to control both platforms in the same way so I don't have to learn two different platform libs. I would also like to say that I will be using DX11.
Take a look at OpenCL, it's an open API that's implemented on a bunch of platforms, including NVIDIA and AMD GPUs.
Also, you can interop with DirectX pretty easily, here is an article on the subject.