Kawai is great in keeping information of old models alive. Start with https://kawaius.com/product/mp8/ if you haven't already and then continue at https://kawaius.com/technology/wooden-key-actions/
For more details about that older actions, see https://web.archive.org/web/20010610005623fw_/http://www.kawaius.com:80/nextlev.htm and https://web.archive.org/web/20040804021127fw_/http://www.kawaius.com:80/digital_actions.htm and https://web.archive.org/web/20091115120136/http://www.kawaius.com/main_links/digital/digital_actions.htm
I owned an old Kawai with the AWAII and it was very good for its time. The MP8 is newer. My instrument had Harmonic Imaging Technology and it was good for its time, but certainly not earth shaking. Not sure you care about the internal sound, the MP8 has a newer iteration, so it'd be better than what I had. Doing a similar sleuthing for the Harmonic Imaging II technology will certainly provide info about it.
I tried the ES8 and I did not like the action at all. As such I would never buy the MP7 (or MP7SE) which has that action. However I would consider the MP8 if I were in the market for a similar instrument.
Obviously you will need to compare price/performance of this used model with VPC1 and MP11 which are its direct competitors. If price is more than half of the competitors, I would not buy the used one. For negotiation tactic, I would use also the price of the MP8 even as I said before I would never buy that.
Also, make sure to check every single key by playing them one-by-one carefully at least at three velocities: pp, mf & ff. Old board can develop problems which you want to know before purchasing. If there is a problem (e.g. not perfect response), you might still want to buy it, but it's a risk and as such you should negotiate the price further down, especially because it may be hard to get it serviced since it's a old model.
Best of luck!