Sonic Defender
Headphoneus Supremus
Thank you so much for your comprehensive reply!
I am looking for a planar that is not so hard to drive and under $800.
My last HP was the Senn HD600. I like neutral-balanced sound but cant stand sibilance
People who have heard both seem to think the 400i is a better treble and bass extended HD600 so that may work for you. Sibilance is actually in the source material, but very treble focused headphones will reveal it more. I don't think the 400i is sibilant per say, at least I haven't heard it being so myself, nor have I read about people saying it was sibilant.