After three days of listening..
The sound is getting better. i can see why many are raving about the clarity and details. i do hope the bass was a bit more thumping. even when playing with my Philips L1 and Marshall monitor, Shure 215 SE, the bass was not as good as my Note3 (poweramp).
Can future firmware 'change' the sound? will continuous play warm the SQ?
I have the standard SE215, SE535 and SE215LTE and both the SE215LTE and specifically SE535 are much better with the DX90 bass wise. For some reasons, the SE215 bass is not as impactful as the other two. My HD600 and Momentum don't suffer from that.
The DX50 and SE215 were more synergetic but through an amp though.
It seems to me you need a better resolving iems/ciems to truly tap into the improved DX90 sq across the whole range. I am convinced the SE846 would be a better match, whish I could have a DX90/SE846 owner verify that.