I have a Carver C-9 sonic hologram unit that I have rebuilt (that is what I do), and have added a switchable Gundry circuit, meaning that this circuit will slighly change the response curve to give a little distance on 'up front' recordings.
Now the Carver C-9 unit by itself has much merit and can enhance many recordings to bring out a 3D presentation that is rare. I am not suggesting that all audio systems out there should have one, but for a lot of applications this is just right. It uses cross cancellation, a bit of delay, and some minor frequency shaping to accomplish its task. Rarely do I advertise this product here, but thought that I might give it a go for anyone who might be curious.
You can view my ad at US Audiomart to what the unit looks like inside and out.
Price is only $230 + shipping. I am quick to ship and have great feedback from this little hobby of mine. Questions always welcome.  Greg