Mostly synergy. The TC7520 absolutely delivers on pace, rhythm, and timing, and has a smooth quality that makes it absolutely easy to listen to- yet it still is able to communicate that Grado edge and bite, especially, when you roll the opamps. Transparency is there, attack is there, really it just does things "right". It's not the sort of tangible, "mids are slightly forward, highs are nicely extended, small lower-midbass hump" sound signature, in my mind, it's the "I'll get arthritis in my leg if it taps any more" type of synergy and presentation. In my opinion, the Beresford is a means of conveying the soul of the music, rather than an electronic signal.
Meanwhile, I felt like the Audio-GD was just a piece of equipment. It was quite a nice sounding unit, and it was excellent when we fed it into the MiniMax. But I definitely got the sense of listening to music through headphones, if you know what I mean. It didn't present bass like the Beresford does, it didn't just flow the mids into my brain like the Beresford does. I like a transparent, lively, energetic sound, and the Compass just didn't deliver for me.
I know that this isn't the usual audiophile speak and I'm not really talking in tangible terms, but this is how I feel. If there are any more specific questions I'll elaborate as best as I can.
