Two specific ways to increase soundstage depth, as you seek. First, increasing the distance of your speakers from the front wall can have a huge impact. If this works in your room, it would be my first move. Second, consider a tube based amplifier. My McIntosh C22/MC275 do a much better job with depth than comparable solid state amps.
Also, are you working with a dealer or other professional? As noted above, this is a really complex process. An hour or two from an experienced person might be well worth the expense