Well, I'll be very honest here, I am somewhat ashamed.
While there is absolutely nothing wrong with going to the top flagships right off the bat, there is ONE fatal flaw doing so:
You will not be able to fully appreciate it.This is true and can applies to many other things.

Anyway, back to my experience.
My first reference is AKG K701 and I am stunned by its capability to produce the high, it turns an absolute basshead like me into one who appreciates high/trebles, it also made me hating low quality bass (muddy and overwhelming).
Then I found a good deal on HD800, pulled the trigger, and I am in another level of world now. I love the neutrality and imaging HD800 produces, it is an absolute perfection of the AKG K701. It is undeniable that K701 is a flawed headphone though, thus the cheap price. HD800, in a nutshell, is a fixed AKG 701 in almost every aspect. Fuller and better bass presentation, balanced treble and they are all very well controlled.
I've always thought and felt that K701 is the start and the end of my journey, until I've gotten HD800, all of sudden, I felt that my journey has just started. HD800's neutrality sparked the curiosity in me, the curiosity to find out the vast definition of "coloration" of many headphones.
With all that said, I still like K701, it has something HD800 don't have and vice versa. The flaw of K701, uncontrolled peak high and lack of imaging is the major turn off for most people I guess. It is very left and right, while listening through HD800 feels like I am listening to a pair of speaker, not headphone.
Now..I can't talk for shit because I don't know shit. Above is just my opinion comparing HD800 with K701.
Fun Fact : I can get both HD800 and K701 with Rm6000 with some changes enough for me to buy a cheap mid entry level amp (ie, Fiio E9)
After seen your pic...you use Sony NWZ-X1000( it's name right?) as soruce + Amp to push HD800 or K701...why don't u add some line out dock to your amp?or X1000 already got line out?