We know it only takes 20W of power for the real thing to work.

Let that sink in. We know it isn’t impossible to run a general intelligence computer on 20W because every single one of us is living proof that it is possible. There is no reason why something man made shouldn’t be able to do the same thing. How to do that is of course a different matter, but it isn’t speculative that it can be done, it’s a direct consequence of our own existence.