IMHO there's no reason at all to downgrade to 8.6. 9.1 is a fine OS, and fixes most of the bugs & crashes in 9.0 of which, in my experience, there were many. It also seems (subjectively, to me) faster and cleaner than 8.6. The only reason *not* to use 9.1 or 9.2 on a compatible machine would be a lack of RAM, which is why I used to run it on my Powerbook 1400.
It sounds to me like someone tried to overclock that CPU, found it crashy, and gave up on it. Lucky for you
Also, OS 9 Helper will allow you to put 9.2.2 on that machine, for even better performance.
http://eshop.macsales.com/OSXCenter/OS9Helper/Framework.cfm?topic=32
/ETA/ I wouldn't 100% rely on the 9.0 cut-off cited at everymac. That may well be the top version listed because it was the top version available at the time the card was issued in 1998. The drivers for Sonnet's Crescendo/PCI should work on the Newer card.
It sounds to me like someone tried to overclock that CPU, found it crashy, and gave up on it. Lucky for you
Also, OS 9 Helper will allow you to put 9.2.2 on that machine, for even better performance.
http://eshop.macsales.com/OSXCenter/OS9Helper/Framework.cfm?topic=32
/ETA/ I wouldn't 100% rely on the 9.0 cut-off cited at everymac. That may well be the top version listed because it was the top version available at the time the card was issued in 1998. The drivers for Sonnet's Crescendo/PCI should work on the Newer card.