iBasso D10 Cobra or iBasso D4 Mamba

I'm looking for a headphone amp to drive my Shure SRH 840's, using my ipod as a source. From what I've heard, the iBasso D4 is a fantastic amp, especially when paired with those headphones, and the price is right.

I was browsing the company site when I saw the D10. From the looks of it, its got more connection options than the D4, but as far as differences go.. thats it?

By no means do I need all of the connection options that the D10 has to offer, so it comes down to the question of which one sounds better. If anyone has any experience or simply some insight on the matter, I would be happy to hear from you. Do they sound different at all, and if so, which one is better and why. If they both sound the same, do the differences simply lie in the amount of connection options? Are the batteries different etc. etc.

Yea they are easy to drive, but thats not really why I'm getting an amp. By no means do I need the headphones to go louder, I just want them to sound nicer.

For the most part, I won't be using the usb connection. I plan to have my ipod as a source, and as such, I will be using the battery. I know the D10 has a re-chargeable battery and the D4 does not; does that affect the SQ?

As for this TopKit, I can't seem to find information on it. That'd be great if you could either explain it to me or give me a link to a page that does.

And I very well might wait for the D12. So far, I've discerned that the D4 is a better performer, and the D10 has more connection options. The question I have is which will sound better, the D4 or the D12.