I had K3003i with a custom cable. I bough it used and the cable had been replaced and the seller assured not sound different to original
 
I loved it. I used it with Fiio X3 2nd Gen. I liked the sound- very flat, great mids, highs and tight base. When compared to AKG K812 with Mojo I could not hear much difference. I thought K3003 was flatter sounding and tad more clearer that K812. 
 
When I connected K3003i to Mojo only I noted what I was missing with Fiio X3. It is much better overall with Mojo direct
 
I sold my K3003 (which I regret now) and the later bought HD800. My first listen reminded me one thing. How similar K3003 and HD800. Both have no body- dead flat and dead honest. Mids-Highs run wild for bad recordings or not paired with correct gear

I have got the Conductor SL 9018 with  CM6693 USB upgrade. As such driver I use is C-Media USB 2 from the Burson website. For some reason Windows 10 drivers does not recognise the USB in Surface Pro. So I use windows 8 drivers. I had few questions and the Burson guys responded in few hours for all. I purchased from a person in US brand new. Actually after 100 hours of burning sound started to improve a lot. Burson support indicated 200hrs for full burn-in
 
My set up- 24bit FLACs (including 192k)-> Synology NAS-> Surface Pro-> Conductor SL via USB-> Audeze LCD-2 with Frazer and AKG K712pro.
 
Even the seller said that AKG-712 would be too crisp. But this set up work very well and I get good base. & 712 sound better than ever with Fiio E17k A2 or Fiio X3 SG. Good sound stage. I have classical and pop rock and all sort of music. Before 100 hours burning 712k had a clear advantage and now LCD-2s are doing very well. I like the highs. clarify and sound stage of AKG 712.  I also have X2 but I do not use it much with Burson as it is well driven by Fiio E17k and X3 SG.
 
I am tempted to get HD800. However I cannot find proper reviews of this combo. Some people says with 9018 DAC HD800 would be too bright. They also said same with K712 but I am loving it. K712 Is only 60+ ohms where as HD800 has wide range and 100hz is peaked 600+ ohms so not sure if Burson will do well. I will ask the question from Burson team of the capability of the unit or will take the unit for an audition with HD800. If there is not much improvement over K712 with this set up I do not want to go there for I will otherwise end up in upgrading the full thing.
 
Please ignore the rating I have given as I have not heard any other high end AMPS etc