WOW!
I just tried my 600 ohm AKG K240M at Ken's suggestion, and they sound really good on the Amphora. The K240M tend to be picky about the amp used, and some amps just don't have the warmth or power they need. Usually my favorite amp for them is my maxed Woo WA6, but I still didn't use the AKG much lately. Now I'm not so sure why that is. True, the 240M don't have the slamming bass of the D2000 or Edition 9, but the bass is at least as strong as the RS-1.
Typically few portable amps are appropriate for the K240M in terms of driving power or sound signature; although the TTVJ portable Millett hybrid was a good match sonically, and the power was just enough to keep me happy. The Pico and Vivid V1 (AD8397 based portable amps) also have enough power to sound loud enough with them, but are still not as pleasing as the TTVJ or the Amphora with them. (the TTVJ went away with my woodied re-cabled HF-1 as partial trade for Stax O2 Mk1 last week, so I can't compare it to the Amphora this time around)
So, the Amphora is really good with the 600 Ohm K240M and plays as loud as the most powerful portables, while having a good balance of warmth and clarity. I don't listen to very loud music, and my normal listening volume with the Amphora and iMod is with the Goldpoint at 3-4 o'clock in high gain. I can max the volume knob at 5:30 o'clock (4 clicks past 3 o'clock) and it is a little louder than I usually listen to music.
This little experiment was a pleasant surprise.