Damit, i just spent like 30 mins writing a post and then hitting back on my mouse by accident and losing all my hard work. Anyways your recommendation to assess what style of music I listen to and what I like/dislike about 650's caused me to revisit it and I have a better understanding now.
I am using Morgan Jones type DIY amp with 3x6N1P valves. Very lush sounding and gave hd595's a very lush and powerful sound. Wouldnt dream of running them unamped but till my GS-1 arrives from Justin I have no alternative choices. Its very good with 0 hum and wide soundstage etc but no doubt its very very (tubey) so maybe a great solid state like the GS-1 from justin will give better synergy with HD650's.
They are great for electronic, there might be better ones but good. (Shpongle, Kryptic Minds, Massive Attack)
They are great for vocals hard to beat. (Yat-Kha)
They are great for folk-rock (jethro tull etc)
They are good for oldschool trash etc (Metallica Load,Reload,Ride the lightning).
Dead Can dance sounds brilliant if maybe just a tad distant.
Coppelius - Brilliant
Russian Circles - gets mashed a little but it is a noise/spacerock so it might be the recording itself.
Unida - Ok i dont notice the cans that must means they are doing ok...
KMFDM - Sound ok no objections here.
Not so good with progressive metal like Tool (10.000 days sounds great "Lateralus" bass separation could be better but I like the vocals again)
Not so good with Guano Apes etc - Again soundwall etc seems to overwhelm the picture somehow specifically guitar tuned in C seem to pose a challenge.
Not so good with Rotting Christ (again this overwhelming rumble effect).
All in all it seems that They are brilliant with vocals and more calm/civilized music but lack something when dealing with:
Melodic Death, Noiserock, Desertrock, Melodic Black, Heavy Metal...
In conclusion, it seems that I am looking for another set of cans specifically for rock/metal. Another thing I am curious about is when mi GS-1 arrives from head-amp what will that do my HD650's.
P.S: It is very interesting when I listen to them, I find them ok but when I just let it wash over me and use them for background listening I find myself reaching for music mentally and its slightly disturbing for me cause I listen alot when I am working.
Also I notice I gave high marks to almost everything so, it turns out they actually are pretty good but there is this strange distant quality to them and I have tried grado sound once and didnt like that either so...just a tad tighter presentation would be nice i think.