I believe I found some in Narnia. You should check it out!
I'm personally not such a big fan of Schiit. Haven't heard any of their products, but from what I heard they do take some rather unconventional approaches in terms of engineering. This may result in a colored sound that many people seem to enjoy, but personally I seek transparency above coloration when it comes to source and amping.
My advice is to let the headphones and the recordings (and equalizers/ other DSP's) do the coloration. Far cheaper, and makes it easier for yourself to sleep at night, since you have to worry less about your DAC and amp.
Quite true, ALL the Schiit amps are voiced to sound warm. Many such as myself like that, but for someone such as yourself seeking neutrality above all else, it's not the route to go. Then again, neither is HD650...could I interest you in some lovely dead-neutral K702's?
Regarding EQ/DSP, if you're using a PC as a source, that makes sense. If you're not, any worthwhile parametric EQ or DSP I've seen cost quite a bit more than a Schiit DAC + amp combined. And several times the cost of HD650. Even at the new inflated prices! So colored amps can be the cheapest way to EQ to your liking, I suppose. Assuming you like the house sound of your preferred brand. I dislike the coloration of Headroom for example.
O2 is dead neutral. You'd love it!