I use two monitors and have the ATI TV Tuner as well. When you activated the video player window, quicktime reset the sound. Under 8.5 with the new version of QT - 3.02, this has gone away and the picture and sound are rock solid. I used the ATI universal installer to force installation of the Rage II extensions and every works fine. I use speed doubler on both machines and have no crashes.
Life is good.
Video score was 177. After disabling Built-In Graphics Accelerator, the score jumped to 230. An added benefit is that these little lines on the right side of graphics loading in Netscape Navigator are no longer there. Another reader said that Macbench 5.0 showed literally identical performance in the graphics primitives tests but a few specific functions scored much better with the extension enabled on his system. It may depend on the benchmark, but the notes on reduction of video artifacts may be reason enough for some to disable the extension.