Can you elaborate more on how the first mod improved sound quality for you? Is this for bassheads? Im reading a lot of bass related features but im not a basshead.

The OPO is an upgrade to the Nexus 5 on all aspects. Sound is more detailed on my OPO than in my old N5 so go ahead and grab it! Bigger storage and better battery also helps. :) 

will be waiting for the full review!

Much appreciated! 

Really? Maybe you tested a lemon unit? Or I got an opposite of a lemon unit because mine sounds great LOL I even preferred it over my fiio x3 so much that I ended up selling the x3. Over at the Oneplus one impressions Thread a guy preferred his over the x5.  In any case I hope someone comes...

Subbed! I would like to know as well. Just bought the Oneplus One for the very same reason that I do not want to carry a DAP around. Pretty satisfied with the One for the moment as it has the best audio experience in a smartphone that I have ever heard but the MX4 Pro has got me interested. 

Got mine 3 days ago . being a huge fan of the s500 this is a significant improvement Sq wise and comfort wise. It is everything Benf said it would be!