You are wrong.
WTF does a simple circuit topology have to do with noise floor? Not saying the F1 is lacking in that regard, but PSRR is not dependent on how simple the circuit is, but rather on the particular topology used. Power supplies also matter for this, and it is certainly possible to have an amplifier with crappy PSRR be extremely quiet simply by taking care of the power supply.
On the issue of the F1's output impedance, it is meant to act as a current source for speakers. When used into an 8ohm load, the F1's output impedance is dramatically higher than that of the speaker, so it actually does a pretty fair approximation of a current source, but into the k1000, it is just a voltage source with shitty damping factor.