RESISTORS

Resistors are used in circuits to impede to flow of electrons.  However, they do more than this basic function.  They also act as a VOLTAGE creation device as well as a CURRENT creation device.  Given a voltage through a circuit does not create a current unless there is some sort of resistance.  Once a current flows through a resistor, a VOLTAGE DROP is created over this device.

In Amplifier circuits, such as FM bugs, the lower the current flow due to a higher load resistance value (output stage), the greater the VOLTAGE drop across this resistor and hence the more POWER that is consumed.

Resistors also limit the amount of the signal that can go through the circuit, such as when used with a feedback circuit, so that the majority of the output signal goes to the next stage.

Therefore, at the output stage, greater the LOAD resistance (e.g.resistor), the greater the VOLTAGE consumed and hence LOWER the POWER transferred.

When the impedance is matched between the output circuit and the input, we have maximum 
POWER transfer take place.

If maximum current is required from the output of circuit1 into circuit2, then circuit2 should have a lower impedance (resistance) as its input into circuit2 as we want maximum current to flow through.