$220 is way too much for E17. looks like EF2A might be the best option for you, despite that extra cost.
Recommendations for an upgrade of the CAL! - Page 2
Ok, here's a quick little "update".
I send an e-mail to Epiphany Acoustics, asking them about the compatibility of the AKG K612 Pro and their EHP-O2D amp/dac.
Here's the response:
Now I know asking the manufacturer/seller directly is a bit of a risk.
I guess I'll made my decision in the upcoming days.
good luck.. really hope everything works out well.. don't forget to share your impressions on 612pro with us.
here is the 612pro official thread.