Thank you for the information :)
I think I may have miscommunicated my question. I currently have the M8 and am using it with my iphone.
Besides the music file quality (96 or 192) how does connecting a DAP (AK100/AK120) which has in internal DAC improve the sound quality?
When a DAP or computer is connected to the M8, the internal DACs of these devices are bypassed and the M8's DAC takes over. Everything the M8 connects to is purely digital. That means, the fancy dual dac of the AK120 doesn't get used at all, when connected to the HiFi-M8.
That being said, these players are more compatable with hi-res files then your iPhone (yes I understand with a little voodoo you can get some hi-res stuff to work). And you already stated that you hear a difference. So the next choice is, which DAP do you want to use as a digital transport?