oh, maybe I'm labeling this thing I'm looking for wrong. What you just described is R in (tot), correct? ... = (R1||R2||Bac(r'e+RL)) (that was from memory!)
I think what I'm trying to get at is that each signal has it's own inherent impedance. The AC signal coming from my function generator has some impedance, and the output of this circuit has some impedance... and what I'm wonder is how is that measured? Or are we indeed talking about the same thing here?