Also, consider that the HE4XX savings over the current price of HE400i (~$219) go toward a component that can adequately power these if you don't already own. Unless have it and want to spend it for a high-end DAC and/or amp, go with a Massdrop-JDS for desktop. You can't go wrong with O2 /JDS setup, or comparable. There are many possible mobile (transportable, really) combinations of DAPs, external DAC/amps, but check an output spreadsheet calculator to ensure they can supply HE4XX with ample drive and headroom for your normal listening volumes. Err on side of more with planars.