"It is not necessairly "harder" to drive a lower impedance speaker - it's more a matter of the amplifier being designed to handle very low impedances such as 2 to 4 ohms"

Thanks guys. One more question. Why do most amplifier manufacturers warn only against using their amps on loads less than 4 ohms? Why would they not also warn against using the amp at higher impedances like 16 ohms or more? Obviously, there are not very many 16 ohm home speakers available (if any), but there are also few speakers rated for 2 ohms and less, so why the warning? Wouldn't a higher impedance (16 vs. 4) be more potentially damaging to an amp?
16 ohm loads might be possible if drivers were wired in certain configurations. Example: A subwoofer cabinet with two 8 ohm woofers. If you had a mono amplifier that was not rated for loads under 4 ohms, you might wire the woofers in series to achieve a 16 (approx.) ohm load. Probably a bad example, but just trying to better understand.

Thanks,
Steve