I too own a 6500/225 and am expieriencing all the symptoms of apple2 (freezes, bombs, gittering movies and mp3's, super instability). I am running 8.6b9 with 96 megs of ram and I clocked my 6500 to 275mhz. Oh and I'm on a cable modem that usually d/l's at 100KB/sec (thats bytes not bits). I have uninstalled QT4 due to the crap that happens on my mac with it on. It even pukes when I run it on 8.5.1.
I found a nasty little bug with 8.6 and QT4 with Sherlock, Apple Video Player, and Netscape 4.5.1. I restarted my mac and opened apple video player, then started netscape, after that I opened Sherlock and did a search. When I double-clicked a search return in Sherlock the netscape window would open and go to the right page. 30 seconds later the Mac would freeze completely! the only thing that would work would be to restart!
I have repeated this bug many times and have tried to stop it by disabling extensions. NO GO! If someone else can repeat this bug on their machine it would be appreciated.
-corwin