I really love my RE400. I currently have these along with a pair of Flare Audio R2 Pro's and swapping one another from time to time depending on mood. I tend to favour RE400 over R2 Pro's most of the times lately. The timbre and natural expansion of the sound on RE400 is as close as it gets to reality IMO. The R2 Pro's might have more bass and a really massive soundstage but that tends to be ''eerie'' sometimes.The R2 Pro's are more about depth while the RE400 sound wider in comparison. Totally different beasts in every sense though I get myself returning to RE400 when I crave for some more ''true to life'' listening experience. I don't expect the RE-00 to be similar to the RE400. They should be more cold and analytical with less low frequency coloration. However, judging by Hifiman's sound signature pattern, they should also sound proportionally natural and lifelike. In a few words, I expect a less ''musical'' but faster and more detailed version of the RE400. If that's the case then I'm sold and they should compliment very well one another these 2 Hifiman siblings Seriously can't wait. BTW, I'd suggest all you loving your RE400, to get a Dragonfly to compliment them (DF version 1.0 comes very cheap these days). The synergy is really OUT OF THIS WORLD either you listen to your music through your computer or through your mobile via OTG cable.