I am looking into buying one of these headphones as they are an upgrade to the sound signature that I enjoy. So I was wondering, between these (or any other similarly priced planars), what should I get and why? I will be running it out of a schiit bifrost and Asgard 2.

I am interested in installing a software EQ, such as Equalizer APO but I was wondering how it would interact with my Bifrost. My Bifrost is connected via USB, however when I install Equalizer APO, it does not change the audio at all. So my understand is because I am bypassing my motherboards...

I'm looking to spend around $200 on an IEM that has a similar U-shaped sound signature as the THX00. I'm not new when it comes to OEMs but I have no idea what to look for in an IEM. 

Any suggestions for a versatile headphone amp around the $500 price range?

Background: Alright, I'm stuck deciding on an amp to power the multiple headphones I own. Currently I own HD650's, DT990 pros, Fidelio X2's, and THX00's. I also am using a Schiit Modi that I am perfectly happy with, as I have not encountered any USB or background noise and do not have the need...