i've read in some other forums of TOM hardware that 10.6 and 10.7 have both problems and many those upgrade their CCC roll back to their previous drivers, so let me know the best suited for each OS particularly for gaming.
<i do't use HDMI>
and one more question, do ATI CCC provide OC for the both GPU/Mem?
if so, can i put to max setting on CCC or what should be the safe level for OCing?
I had issues with 10.6 and have yet to try 10.7
The Overclocking depends on the card, yes you can access both the GPU Core and the Memory from CCC. You need to open the Overdrive section by clicking on the padlock.
There is an Auto Tune option if you like but it does take a while and your screen will go all green/yellow/red i think it is and wont respond for a good while.
If you choose to do it yourself then just look up a decent online guide to Overclocking your card.