Let's say that the knower is physically, you; and that the known is something you know conceptually -- in essence we are talking about your body and soul.
Add to that your identified "problem" ... the obvious problem of knowing that our impressions are true representations of reality ... and we're talking about the split Ayn Rand identifies as the "Soul-Body Dichotomy," of which she writes ...
As products of the split between man's soul and body, there are two kinds of teachers of the Morality of Death: the mystics of spirit and the mystics of muscle, whom you call the spiritualists and the materialists, those who believe in consciousness without existence and those who believe in existence without consciousness. Both demand the surrender of your mind, one to their revelations, the other to their reflexes. No matter how loudly they posture in the roles of irreconcilable antagonists, their moral codes are alike, and so are their aims: in matter -- the enslavement of man's body, in spirit -- the destruction of his mind.
There is no "split" except at death. The soul is the act of the body.
From this quote it doesn't appear that Rand understood Aristotle's conception of act and potency.