Q. After reading your recommendation I ordered the Hifiman HE400se headphones from headphones.com for $109. Now that my order is placed I am reading that a headphone port is insufficient and you really must use a headphone amplifier with these planar magnetic models in order to get adequate loudness. Is this true and if so, what do you recommend? —K.T., Atlantic City, New Jersey A. I received quite a few emails similar to yours. The answer depends on what kind of headphone port. If it is the headphone port on a component receiver, amplifier or preamplifier you will get more loudness than you w…