As this blog address music lovers ready to invest (some) money in their (portable) hifi system, here is a suggestion to help you increase dramatically the way you enjoy music on you pc or ipod : a headphone amplifier + digital-to-audio decoder.
I did some research and bought one recently : a small "made in Germany" headphone amp that works on battery or USB, designed by Jan Meier under the brand name CODA.
The result is blasting : though my main pc has a pro 24bit soundcard, my laptop has an average one and listening to music with has never been satisfactory (despite my Grado Headphone). Plugged in the USB port this headphone amp bypasses the native pc card thanks to the Digital Analogic Converter (DAC) of the CODA (a Texas Instument) and delivers superb sound.
Moreover the CODA has a proprietary cross filtering sound enhancer that gives a smoother sound and reduces the excessive stereo effect that headphone mechanically create. So when used with the ipod (plugged directly to the ipod dock to avoid the poor filtered sound from the jack) it is a powerfull way to increase sound quality. And it is fully portable.
for those who were lacking ideas for christmas give a look at the cute CODA MOVE3 at Meier Audio