So let us get the good news out of the way: targeted US sale of IE 600 will be May 12th (preorder) and release on May 24th (shipping of available stock). If you're wanting IE 600 and hoping MTW3 will fill the gap, they're just too different in terms of application and core features to be an interchangeable recommendation. MTW3 are available to pre-order
now with a target release of May 10th.
While there is some shared DNA in a Momentum True Wireless series set and IE 600, I'd pick the IE 600 for
listening with intent over MTW. For context, I use the MTW2
daily for calls, music, and YouTube TV. I absolutely love it. It's remarkably close to a wired sound with the right app. I feel anxious when it is not with me. It's a much higher quality listen than freebie wireless earbuds, and has the "Sennheiser Sound"...but an IE 600 owner will not mistake the two for each other.
The MTW3 signature will sound similar to existing MTW2 and MTW sets, but with better noise cancellation when you need it. For those needing the best-sounding true wireless earphones because they don't like what they have, or they've been bit by the audiophile bug, or want their first set to be reaaaally good, get the MTW3 without hesitation. MTW3 will be darn good and for your wireless needs, will get you
closer to IE 600 sound than anything else that is true wireless.