I bought this for £69 on offer.
-Very good sound for the size and price. Better sound that my Nokia N8 and new laptop using latest mobile Realtek chip.
-If your music has been properly recorded (meaning the source volume is strong enough), this will easily power (give enough volume to) high end Hi-Fi headphones such as the sennheiser HD650 and Denon AH-D5000.
-This is able to power my Klipsh X10 headphones that I bought to the maximum of their quality.
In terms of sound quality, without taking its low price into account and testing it with Denon AH-D5000 closed cans, comparing to a Marantz PM7003 amplifier with the PC as source:
-Bass is not strong but detailed enough at this price on flat EQ, the EQ in this device can make up for this, if you turn up the bass.
-Tremble is on-the-spot for me (soft and hearable) but the mids are slightly on the background which causes an impression that the "sound is not alive".
-The soundstage is kind of reduced when compared to the sound produced by a Creative X-Fi Titanium HD or the on-board latest ALC (Realtek) desktop sound chip. It is still a better performer than the laptop though.
-The sound of the FiiO is slightly muffled, even when listening with cheaper headphones though the issue is not as much pronounced in this case.
Bottom line: At £70, this device performs really good and should be matched with headphones maybe up to £150 but no more. If you are looking for something better than this you would have to look at £200+ mini dac-amps for headphones from HTR, Audioquest or Meridian.