Looks like a lot of people have jumped on to buying the FX850s. I purchased them at ~$400 shipped several weeks back, and I've got to say, even at that higher price tag it's been worth every penny. For those that picked them up for ~$300, thats an absolute steal!
I would recommend trying the J444 mod that was mentioned earlier in this thread for those who haven't tried it yet. I've been using TF10 tips plus J444 mod and it tames the bass down a notch and balances out the spectrum a bit as a result, especially during the earlier stages of burn-in. It doesn't take very long to do (probably took me 5 minutes at most) and is completely reversible so long as you have some spare tips lying around to sacrifice. The FX850 sounds great out of the DX90, but it's completely sublime out of the headphone out of a loaner Anedio D2 unit that I've had for the past 2 weeks. I didn't know that kind of soundstage was possible in an IEM. I can see the FX850 keeping me happy for a long time- less time perusing FOTM threads and my wallet can finally put some flesh on it's bones
#winning