It would perhaps be a fair comparison to make, but since I've yet to hear the J13 v. J16 myself it's a mystery I'm left to ponder. Will try to make it out to the next big show that has universal demos so I can give them a listen.
The C4 actually pairs poorly with the O2/ODAC. I tried it a couple times and something about the pairing makes it exhausting to listen to. I just purchased an Ultrabook, so will be looking for a mid-tier portable amp/DAC combo to pair with the C4 if it doesn't sound acceptable straight out of the box. I'm not incredibly worried about the amp/DAC pairing as the C4 sounds pleasant straight out of my current laptop, but I do think having an appropriate source can make for a significant improvement.
I've had a chance to listen to the C4 paired with a DX100 and thought it was an improvement over the Clip+ I'm currently using; there were subtle differences as well, but the main win was dynamics. The Clip+ is an amazing player, but the difference between soft and loud parts of passages are not as wide as I've heard from other sources. The DX100 does this significantly better, the only question being is it $700-$800+ worth better?
As my Ultrabook purchase was in that price range, the current answer is "No!" as I passed on the DAP for it.
Glad to hear your impressions were finally accepted! Here's hoping you receive your C4s shortly. Killer avatar by the way. :) Kyuubi was quite the character. Cute little critters with venomous intentions are interesting to say the least.
Hmm, that is kind of disappointing I guess. I should be getting a new dac/amp that I "ordered" maybe this summer/spring. Well, in reality it's a DIYed combo that is made to be similar to the O2/Odac combo. Meh, I'll just take the chance and see how it turns out. I definitely don't expect any drastic changes, but hopefully it won't turn out exhausting. I've never had an exhausting headphones so I'm not too sure what that means. Oh and thanks for the compliment. :3