I hate to admit it, but "full potential" on the HD 6XX requires a lot more amp than that. I am not saying it won't sound good though.
Let me put it to you this way. I enjoyed HD 6XX out of a Magni 3. The HD 6XX showed improvements even up to the $8000+ DNA Stellaris. It really does scale that far.
Now, if you're concerned about power, the Mayflower ARC should be enough.