On the one hand, any loudspeaker amplifier with feedback is going to have very low output impedance (minimum acceptable damping factor of 20 with an 8 ohm load or .4 ohms max).  So for at home, AC powered use just hook your headphones to the speaker outputs.<p>On the other, things do get interesting with low power &#x2F; battery powered amplifiers, for example where they use a low power OP-amp for headphone drivers.  For this case, the article is very relevant.<p>Heh, or get headphones with nearly flat impedance, for example Sony MDR-v600: <a href="http:&#x2F;&#x2F;www.cliftonlaboratories.com&#x2F;headphone_impedance.htm" rel="nofollow">http:&#x2F;&#x2F;www.cliftonlaboratories.com&#x2F;headphone_impedance.htm</a>