I've heard lots of speakers, and frankly Soliloquy does a pretty first rate job of soundstage width, depth, etc. Have you tried pulling the speakers further out into the room(I find Soliloquys in particular need breathing room to image/soundstage at their best)? That will certainly help if you've only got them a few feet from the back wall(assuming you have the flexibility to do so in your room). You might also consider trying Cardas Neutral Reference or AZ Silver Reference interconnects(Soliloquy uses these at shows) that may be a little clearer to the back of the stage than the Goldens(others with more experience with Cardas cables may have more thoughts on this).
Other speakers I've heard that do a good job in this area are Silverline Sonatas/Sonatinas, Vandersteen 3A/5, Coincident Technology Super/Total Eclipse, Audio Physic Virgo, Thiel CS1.5/2.3/3.6.
Just some thoughts, but I'm surprised to hear you're dissatisfied with the soundstaging abilities of the 6.3s and so I'm not sure changing speakers is going to give you what you're looking for--but it's always fun trying anyway. Best of luck.
Tim