Do I need BOTH amp and pre to be sonic holography?

Carver's system, otherwise known as the 'Sonic Holocaust' was a way to clean up the stereo image.
When recording say....just for example.....a singer and band with a pair of microphones, each mic will get information....somewhat time delayed, perhaps, from the opposite side.
Sonic Hologram will subtract right side information from the LEFT and left side information from the RIGHT. This eliminates the 'crosstalk', if that's the right word.

Polk did the same with speakers a few years later, by having a pair of midrange drivers about 6" apart horizontially. The distance was decided by the space between ears.
They fed signals between speakers to accomplish the same 'subtraction' and used the distance between drivers to account for the time delay.

I never heard the system. I'd like to hear it with headphones.

The phrase was something like 'Interaural Crosstalk Delay'.......

In my (now ancient) messing with backchannel phased speakers (no delay) I was able to get great results by using a 2nd amp and wiring a pair of speakers IN SERIES between positive poles. Live recordings were LIVE.
In those days the system was a pair of JBL4311s in front w/ an SAE power amp and a pair of RSL3600 Studio Monitors and a Kenwood KA7100.

I STOLE the idea from the then popular DynaQuad circuits I saw.

yes, the head causes additional time delay.
It also causes the 'downstream' side to get fewer high frequency part of the sound. That's the reason for the 6" speaker seperation on some Polk models seeking to mimic this circuit.

In nature, the time delay, spectrum difference, loudness and several other things are all 'cues' to location and direction and distance.
VITAL to survival.