Don't worry about 24/192 and upsampling - 24/96 is more than high enough. The E09k has significantly more power than the E17 to drive the MadDogs very well. Its 10 ohm output impedance means it probably won't pair well with your IEMs, but you have the E17 for them so it's no problem. The nice thing about the E09k for you is that it will let you use the E17 you already own as a DAC. I think it's a good way for you to go.
Thank you for taking the time to reply.
I also thought of that... To keep my E17 and complement it with an E09K.
My portable rig is an iPod touch, connected to a Fostex HP-P1 that serves as the DAC and a Fiio E12 that serves as the Amp.
I really like that setup, that is why I am thinking about the HP-A4 for desktop setup.
How do you compare the DAC chips and implementations of the ASUS One, HP-A4 and E17?
Does the ASUS deliver that much bigger sound quality and would the Mad Dogs be able to take advantage of it?