The 009 for me always had better 3d positional sound. Instruments and vocals were placed either wider apart, or closer in depending on the recording. It had a greater breadth of how it could place sounds in 3d space.
That is why it always surprises me when people say hd800's one thing over 009 is soundstage.... It might be I don't know what "soundstage" is tho.
Of course, the Carbon amp is known to give great soundstage for Stax, maybe if I had the hd800 on a $5000 amp it would beat the 009 in soundstage?
For me the hd800 killed the 009 in microdetails. I'm not big into stuff like that, because you have to reaaallly be listening to the music closely to hear stuff like that. I'm more about enjoyment from listening to music, not listening to music like a college lecture trying to pick stuff out.
With that said, the clarity, raw resolution, and transparency of the hd800 were so much greater, I decided to sell the Carbon/009.
The current amp I'm using with hd800 is the Taurus mkii.
EDIT: As always YMMV. As is obvious from the post right underneath mine.
I just see so many posts definitively saying Stax TOTL is world TOTL for headphones. I dropped $10k into that bucket, and came out objectively enjoying hd800 more.
Lotta group think in this this thread, which is fine, it's Stax thread. Why would anybody trash their $5k+ rig lol.