Those are the two headphones I still have, too. I had Aryas, but sold them. They were better, but not better enough to justify keeping the money tied up in them. You can EQ both the 6XX and the 400i to the Harman target, and they'll still sound very different. I prefer the 6XX with these EQ filters. I prefer a flat bass response to the Harman bass boost on the 6XX, but prefer the Harman target on the 400i.

Even with EQ, I don't think the 6XX "wow" me. They're magic, often, but never exciting.