Tim, It sounds like soundstage is your main concern. While many things can affect that, I'd focus on power conditioning, speaker placement and room-tuning.
Power conditioning will lower the noise floor. That allows you to hear more detail, including ambience, and tends to make the soundstage more expansive & realistic. (IMPORTANT -You probably want to exclude your power amp from conditioning. Most amps sound best 'straight into the wall'.)
Speaker placement can have a profound affect on soundstage & imaging.Quick Tip: I find that many people use too much toe-in, and that will shrink the soundstage. When asked, they say they like the 'focus'. But what I often hear is a compressed soundstage - and depending on the speakers - a bit too much treble.
It's best to start with a pretty good room... if you can. I recommend restraint in room-tuning. Too much can make the sound 'dead'. You mostly want to deal with early reflections and bass bumps.
I hope that helps!