For a comparison of the NE-600X vs 700X vs 770X, see here:
http://www.head-fi.org/t/623137/review-comparison-nuforce-iems-ne-600x-ne-700x-ne-770x
quick summary:
- bass sloped sound
- tiny fit
- great clarity/detail
- fantastic sound for $35 and easily the top choice between the 600/700/770X
