you will never have to buy OS 9 (even when OS X Final comes out) to use OS X. You will only have to purchase and install OS 9 if you want to run any "Classic" applications. If you don't want to run any classic applications thats fine, however I think it is extreamly unrealistic to think you are...
Trueman_Akamai,
I have a power tower pro 250 (604e), let me know if you get the beta to work on your 8500 and how, so I can try it on the ptp250.
Thanks
Greg