I'll answer the questions asked - sorry, hadn't been back since I originally posted.
I've been burning in a new pair of headphones and have left the DacMagic Plus on for 24 hours straight. It was slightly warm but not hot.
The headphone out on the DacMagic Plus was better than I expected. It drove both the HD650 and AKG K702 quite well. However, its no match for the Burson. Stronger bass and better dynamics with the Burson.