Another hugely important album that I don't think has been mentioned yet is The Orb's Adventures Beyond the Ultraworld, particularly "A Huger Ever-Growing, Pulsating Brain..." (1991). While not psybient itself, it certainly seemed to bring an awareness of electronic chill-out music to people who previously didn't know the genre even existed (remember, this is pre-Internet, so you couldn't just stumble across this stuff on YouTube, LOL).
Then in the early 90s you had what was called "ambient dub". Tracks like "Spectral" by Higher Intelligence Agency (1993) would almost certainly be classified as psybient if they came out today. A similar band is A Positive Life. Tracks like "Bathdub" (1994) sound very psybient to me.
Another early psibient-ish band is Optic Eye. Tracks like "Wobbling in Space" and "Far Out Race", actually pretty much most of their Light Side of the Sun album (1994), sounds very psbientish.