Dont know who advised playback separately - but using playmode 70-76 onwards is probably the simplest way of playing a movie with audio.

The FPS counter will disappear, because catalyst prioritises audio playback when using these playmodes (70-76) - i.e. it plays back at the same frame rate as the clip with audio was encoded - no matter what your system frame rate is set to. This is to ensure that the audio playback is flawless and sounds like it was intended.

So the best way to playback audio with a video file is to encode both together as one movie (eg AIC codec) and use playmode 70-76


However - you should also check the spec of your graphics card and read this post:

samsc.com/showthread.php?t=1908

ATI 4870 / 5770 / 5870 have driver issues is 10.6.6/10.6.7 - and you get very poor performance when using catalyst.
You should change your graphics card to an Nvidia card which does not have the same problems.
The Nvidia Quadro 4000 is the best performing official card available if using Snow Leopard (as of May 2011)

Do get back to me if you need more help

Simon