Neutral needs a reference point - or the neutral is per definition the reference. I would say that the Gungnir presents a tad more coloration than the V800 and the M51 from NAD. I.e. among these three, I would not say the Gungnir is neutral.
Coloration can often be a good thing and for many head-fiers they seek exactly the right amount of coloration. Others don't. What to prefer, is not solely up to the listerner's preferences, but also what kind of music they listen the most to. Some like the HD800. Some the LCD-2. And so one.
I would put the V800 and the M51 in the "HD800" segment - and the Gungnir in the LCD-2 segment of sound coloration. Stupid analogy - I know - but better than none.
Fun factor = the right amount of coloration = toe tapping experiences. The NAD M51, or the V800, in a combination with the right amp will of course make toe tapping happen, but for me they needs to be combined with some coloration. Cf. the V200/V800 + LCD-2 combo.
If I was allowed to keep one DAC of the V800, M51 and Gungnir: The two latter had to go. Not because they are not good. They are very good, but the V800 would be a one-stop-DAC to both the V200/LCD-2 and the Mjolnir/LCD-3 for me.
That simple. That complex. That subjective.
PostScript: I know that opinions on the internet are easily blown out of proportions, so I'll say this: I find all these 3 DACs to be very good. I like the versatility / flexibility the M51 and V800 has over the Gungnir - and that fact does not clutter my view of them sound wise.
Edited by Loevhagen - 10/26/12 at 7:46am