Sound Quality Update:
I did a long A/B comparison between my laptop with Foobar and USB to the iBasso D1 and the Q5W with SPDIF to the D1. First both were set to flat EQ and no DSPs. Since the iBasso was set to the same volume for both, SPL levels were the same. The exact digital files were played from both sources.
At first Foobar had a more musical and richer sound. Speraration was less and soundstage was tighter. Melodic notes were expressed in such a way that they came in front of the complexities of sound below. The bass was very smooth and clean but lacked some punch and reverb. It was more recessed and less detailed. The highs were very crisp and a little bright. A rasp sounded like a rasp with the rise and fall you expect.
The Q5W with SPDIF had a greater soundstage and instrument separation was very wide. The bass had more punch and reverb, with greater detail and tightness. The mid bass seemed to cloud the mids a bit. Melodic tones were no longer put in front, but fell into middle with everything else, competing to be heard. Likewise the highs were more recessed and put more in the background. A terrific amount of detail was there, but the notes seemed to be in competition with everything else. I would say the Q5/SPDIF was more wider, detailed, neutral and colder. Foobar/USB was more compressed, brighter and musical.
Then I added the Crossfeed DSP to Foobar and listened again. Well what would you know? Soundstage became much greater and instrument separation became wider. I then added a room reverb DSP and the bass became more punchy and tight. The highs became more recessed and melodic tones fell back into everything else. Comparing Foobar with the DSPs and the Q5 now, they both sounded more similar. The Q5 sounded better as I think the room reverb DSP in Foobar had too much impact on the sound. With just the crossfeed DSP in Foobar engaged, they both sounded really good, with Foobar still leading because it had a more enjoyable musical sound. The Q5 still had greater clean detail and separation. The Q5 has such a clean battery power supply that it results in a more sterile and clean detailed sound out. The Q5 is more solid state sounding.
The net result is that Foobar still rates as the best sounding source compared to the two. However, the fact remains that it is impractical to carry a laptop around to listen to my music on the go. For that the Q5 is the next best thing. By tweaking the EQ settings and bumping up the mids, I was able to bring out a more warmer, musical sound. The shear amount of detail and great soundstage makes the Q5/SPDIF/iBassoD1 almost too revealing at times. When a high quality digital recording is fed through it, it sounds almost too good to be true. It is like the first time you listened to your first set of high-end headphones; you hear things you never knew were in the music before. The downside is that no one part is over emphasized by much and this makes it sound a little less musical. However, once you get use to this kind of sound, this kind of detail is highly rewarding.
Also, more impressions rate the Q5 as having better sound quality over the Cowon D2.
Sound Qaulity: Q5 Versus D2 - iAudiophile.net Forums