After owning both for some time I will update (or re-iterate) my impressions. Basically I mostly agree with Tyll on the differences between the two. The Flow (open) is more smooth, easier listening, more euphoric. The Utopia is punchy, dynamic, forward in direct comparison. There are less dynamics with the Flow but it's easy to listen to for longer sessions. Both are very resolving without emphasizing treble and I find the low distortion very good on both. The Utopia has the edge for detail retrieval and speed to my ears. Both feel overall balanced to me with regard to frequency response. The Utopia has slightly more mids/lower treble and the Flow has a little more upper bass. Both are easy to drive and reveal source gear well. The one thing the Flow doesn't do as well is dynamic punch, but then again the soundstage feels slightly larger with the Flow. For me neither headphone is going anywhere anytime soon. I listen more often to the Flow simply because I get too distracted when listening to the Utopia (too much of a good thing?). The Utopia commands my attention while the Flow allows me to enjoy the music immensely without completely demanding my attention. I'm still waiting for notice to upgrade my ETHER C to Flow C (first day register here... Dan?) so I am only comparing the open version for now.