Haha I sold my HD598 a while back but hearing the way you wrote really makes me want to get it back if only just to compare side by side with my HD800. 
 
The HD598s are great for the price but do you really think that they are comparable to the HD800? 

I can agree with you, Danny, I just have owned one pair of HD598 and it sounds amazingly with my ampli dac Matrix. I can compare it with my beloved Denon D2000. The HD598 is lacking a little bit warm with my style of music compared to my D2000 or Corsair Vengenance 2000, but i think i will have it burned more to see if it sounds better.  =D

I use the HD 598 and get what you say about graininess.  You may have saved me a lot of time and money messing around with HD sources.

The HD 598 are great when I listened to them, it was well burned in so I didn't notice graininess. I have a pair of HD 555 and they sounded really grainy in the mids(literally sounded like real grain, it was weird as I never really heard something like that since) when I first got them the grain mostly went away after a month or something but is still there slightly. The HD 800 bothered me with it's highs when I heard it, I had to cross it off my future buy list because of the treble.

well I have a lot of the Sennheiser series including the HD598,HD650,HD800,HD600(before, sold now), Amperior, and so on but I'm not so sure about the detail thing. It comes no where close the 650 or the 800. 600 sounds more like the 800 in my opinion. The 800's soundstage is MASSIVE, 598 is nice but it isn't really that close. Just sayin. Now I do like the 598 for some music like Adele but then I have my Grado so in the end these are sorta looking for a new home atm.

also maybe it's because of the amping. I don't amp the 598(usually). But then I use the Graham Slee Solo SRG2 with the others including the Grado.
For the money though, it is very nice and also the lack of neccesity of amping it.

just to say, yesterday night, i watched Gravity film of Clooney using the HD598, I was alone in the dark and it was the first time i have to turned my head behind for sometimes because i had listen to some sounds on my back. It was an interesting feeling, and it had never happened to me when using my Denon D2000 or my Corsair V2000 or some low cost Sennhen HD series like 202, 201, ... , haha. It is cool.