Whoa! Soundstaging depth is predominantly the purview of room geometry and listening position. If you set up a fairly small triangle with lots of space behind the speaker plane you have the potential for a VERY deep stage.
If not, then only subtle spectral colorations (various speaker choices, cables, dedicated lines, etc) can provide some aspects of depth. One interesting extension of this is to "mirror" the geometry by using multiple speakers in an HT arrangement, where-in the "depth" exists predominantly in front of the speaker plane which is usually back near the video, if not on the front wall!
I'll let the eyebrows relax by certainly acknowledging that soundstage WIDTH and horizontal detail are provided predominantly by very well matched stereo pair monitors, especially when carefully positioned to optimize sidewall reflections. (Indeed, some reflection can be desirable to balance off-axis midrange vs tweeter responses (flare), and to widen the stage beyond the speaker positions.)
I fall back on my current systems by example:
2 channel uses a 7.5' equi-triangle in a 14x24x8 room. Asymmetrical, damped sidewalls (stuffed furniture, angled fireplace, window array broken up by molding, etc.) a few feet away, but with 10 feet space behind the speaker plane (no choice...Steinway B sitting there). Soundstage depth is remarkable. Easy to accomplish with any decent pair of monitors. By assuring VERY-WELL matched clones of drivers (Verity Audio Parsifal Encores), and slight tuning of sidewalls with throw pillows, etc., as a function of recording balance, I routinely achieve a 15' wide stage that easily goes deeply past the front wall out into the bushes! But it's more about the room geo than the optimization care I use to tweak it, methinks....
HT system: Spendor front trio (S3/1p and SC3) 1-2 feet off the front wall, flanking TV, with Boston VR-MX rears 15' back in a 14x24x cathedral 8-10' ceiling, VERY undamped. Spendors chosen because they're forgiving of bright HT mixes, a live room, AND their drivers are pretty carefully cloned for stereo imaging too. Yet my nearfield listening position yields NO depth beyond the speaker plane (I know, the TV doesn't help), and a 3D "space" erupts only when the rears are called into play (which the NAD receiver's "EARS" coder does well on 2 ch, thankfully).
(Further, I often listen to this system for background FM while on the computer at the opposite end of the room, where the 5.1 array is now FULLY "behind" my back. I have compared straight 2ch to 5.1 "coding" from this position often, and almost always prefer the spaciousness of the 5.1, since the "rears" now act as "extra-far" left and right speakers, as the main Spendors are 20 feet away.
So the perspective is having lots of "depth", but only in FRONT of the speaker plane....
As an example, if I'm listening to a live FM feed of the BSO at Symphony Hall on Friday afternoon, I can walk back and forth between the NAD "fake" 5.1 in front of me ( oh so BIG!) and the much more accurate 2 ch deep stage behind the speaker plane. The former is somewhat like my cheap-but-good 2nd balcony subscription seats...the latter like the pricier front orchestra "Brahmin chaises".
Sometimes programming material, mood, etc., dictate my preference. Usually commercial "multi-mono" rock and jazz recordings are so artificial that they're more fun in the sloppy "backwards" 5.1 HT system in this lively room. However, all acoustic 2 mike jazz of course sounds better in my $$ 2 ch ref system. And an odd rocker like that Stones' "LIVE" disc sounds phenomenal on the ref system. Stage depth back to Canada!
Sorry for such a long post, but I just wanted to emphasize that speaker placement/room geo is the predominant requisite for stage DEPTH creation, further optimized by speaker pair cloning and component quality only secondarily.
That being said, for under $2k, my limited commercial-speaker experience points to the Revel M20 for accuracy in a well-damped room, and Spendors for a more forgiving spectral tilt in a livelier room. There are of a course a myriad of choices, some as posted above, but paying attention to L/R speaker matching is important, and unfortunately well-practiced by only a few manufacturers, especially in the lower price ranges. It's interesting to note occasional disappointments that occur when someone insists upon buying a NEW pair of speakers instead of buying the dealer's demo pair, which as often as not might be randomly "matched" better! Driver sensitivity and response specs certainly have tightened as a rule throughout the industry over the decades (thankfully), but I still pay careful attention to makers' claims that drivers are referenced to tight response norms...it makes a BIG difference in soundstaging....
Sorry about the length of this post. You got my second cuppa joe! Ern
