Speaker - Electrical Characteristics
Does the stamped “8 ohm” refer to the total impedance at some standard sine wave frequency, e.g., 1 kHz?


Only approximately. It's a "nominal" value, but the actual value can vary over a rather large range.


  If so, does that mean that when driven at 1 kHz that the total impedance may be expressed as 7.2 + j0.8 ohms?


No, impedances don't add that way, because of the phase angles involved.

If we assume that the speaker's impedance at 1000 Hz is exactly 8 &Omega;, then the reactive component is:

$$X = \sqrt{8\Omega^2 - 7.2\Omega^2} = 3.5\Omega$$