I agree with the assessments of the 128 above and I would add that tube selection (assuming you're using the stock EH's and feel that the highs are a bit surpressed) might make it sound more expansive in some systems.
Now the comments you will hate but I'm just trying to help. If you really want to increase your soundstaging, especially the sense of depth, and assuming that your systems photos accurately reflect your system set up, try bringing your speakers out into the room some more (keeping them in in an equallateral triangle with your listening chair). If you like it better, but its not acceptible to important others, you can always make subtle marks on the floor where the speakers sound best and simply pull them out to that location for critical listening. FWIW.