I' don't own myself any Summit-fi amp or dac but I really can feel HD800 sounstage as cavernous too . Differences between mixes becomes obvious too. Sometimes music come from My nose , sometimes Music comes from a large and deep area with the soloist quite near and orchestra well layered beyond.
Nevertheless, I haven't compared to a Beyerdynamic T1 or Hifiman HE500 that are often considered as kings of 3D Soundstage.
Edited by Sorrodje - 9/28/13 at 1:59pm