Originally Posted by SilverEars
To me it doesn't sound dark. It doesn't have sparkle or tinny or forward treble the DX90 has. That doesn't mean there is no details because of the lack of forwardness, but details show since the bass doesn't over take it or it seems neutral for the most part. I found DX90 mids to be not that clear, possibly because treble and bass stood out.
My ears can hear details with 650 and TG334 which people think are dark. Moment of truth will come when my NT6 arrives, the judge.
My NT6pro likes to pair with my X5 much more than my DX90. The X5's black background, forward presentation, and extra power play into the NT6pro's extension, dynamics, and clarity extremely well. The textures from the pairing are very rich sending shivers down my spin. The DX90 just cannot drive the NT6pro as well even though it sounds great when not in direct comparison. The X5 paired with the NT6pro actually sounds better than my desktop setup which has not happened until now.
The X5 and DX90 are both excellent DAPs, but neither are going to blow you away until paired correctly with the right headphone and right quality of music. I find the music to be the biggest bottleneck to audiophile sound quality, but with the right music and the right headphone, I think you will have trouble using anything less than ether of these DAPs as you will become spoiled very quickly. My NT6pro and LCD2s really show off what these DAPs can do while playing the songs on my short list of favorite audiophile quality songs. However, poor quality music or lessor headphones such as my HD595, Monster Coppers, and TF10s really hold down both DAPs making them sound more......ordinary.
BTW, poor quality music is more about the mastering than the file format for me. I have MP3s that sound better than some 24/96 high definition files. However, if those MP3 were available in the HD format, I would upgrade them knowing that I am losing part of the file information with losey files. When you hear a good song/mastering you just know it, it just pulls you in emotionally with its magical powers regardless of file format. Those are the songs that make these DAPs with the right HP pairing sound extraordinary.