Headphone Amps

I originally started the DIY Audio scene with an interest in high quality headphones. My first project as Pete Millett's Low Voltage Headphone amp, followed by the Maple Tree Audio's EAR++ kit. Both these amps proved to be very nice to listen to through my Sennheiser HD-650's. And I continue to enjoy the intimacy of the listening experience that headphones offer. My upcoming trip has once again sparked an interest in headphones, but this time, in the mobile/portable hi-fi direction. So now, how can I mirror the quality/result of my current setup so that I can take it around with me? The search is now on for a small, low-power consumption (i.e., battery operated) and highest quality mobile/portable headphone and headphone amp combination. Some of the amp work has been extensively covered by sites such as Headwize and Tangentsoft to name a few of the popular sites. This would be a good starting place. The classic CMoy design is a very simple design, and having built a few of them, a great place to start. In regards to headphones, it appears that 'In Ear Headphones' or 'In Ear Monitors' are the best mobile solution. From reading various reviews, Etymotic ER-4S appears to be one of the best sets of in-ear headphones that are priced within reason (less than US$300). Other contenders include Shure and Ultimate Ears. The Headroom site offers a great selection of headphones, amps and information. Surprisingly, there are a number of Australian sites that stock various headphones and related equipment; Wicked Digital and Headphonic are some of note. More notes and progress to come!