I have the Alps pot. Regarding the hd800 combo with the mini, I'm not sure how useful my impressions would be. I always EQ the hd800 with Sonarworks. That plugin is essentially trans-formative to the signature of that headphone.
I have extended family in town for a few more days, so I won't be able to really dig in for a comprehensive review until next week. I will say this though. The Mini has lived to up to my high expectations and in some ways exceeded them. I couldn't be happier with this purchase. I've always told others that the hd650 scaled exceptionally well with better upstream gear, but I honestly didn't know how good it could really sound until I plugged it into the Mini.