I've been auditioning the 8's paired with an iPhone 6S, 6S + Oppo HA-2, Note 4, and Note 4 + HA-2, as well as HA-2 w/ PC. Audio files range from iTunes music, Google Music, Tidal, and Onkyo HF Player with DSD256 sample files from Oppo.
My initial impressions are as follows:
The iPhone 6S alone is pretty darn decent. Sound is excellent.
The iPhone 6S + Oppo HA-2 provides a small improvement. Slightly wider soundstage, a bit more space, and better dynamics. It's hard to say that the pair is really worth the extra bulk. Sometimes I just want to use the iPhone without the HA-2 because it sounds "good enough". Ha. I'm not sure that's a thing with these IEM's. The benefit obviously comes from the DSD/FLAC decoding ability. But to be honest, I'm not sure my ears are really good enough to hear a big difference between 320kbps MP3/AAC and DSD. Let alone DSD64 and DSD256.
Note 4 alone... mmmm, Meh. I use V4A and some rooted tricks to improve sound quality, but it's not quite as good as the vanilla iphone (I also use Equalizer everywhere for iPhone)
Note 4 + HA-2 provides a more noticeable improvement. Definitely worth the investment when these two are paired. No problems with USB Audio for the applications and the android build that I am running.
Oppo HA-2 with PC is obviously a huge improvement over built-in sound on a Gigabyte Z97-ITX. I compared against my Focusrite scarlett and the Oppo wins, barely.
I haven't changed my filters out yet (not sure if I will). I'm using the 2 dot olives and isolation is great... I've had them in for a couple hours and my ears notice a bit of fatigue.
Still trying to decide if high-gain vs low gain makes a difference.
Also, wondering if the HA-2 is really giving the 8's what they need. Output impedence of the HA-2 is just not quite enough for the 9ohm 846's.