I prefer to lock the card in its specs as set by the manufacturer. For the asus card I use these extra options for cgminer
--auto-fan --gpu-engine 800 --gpu-memclock 1250 --temp-target 64C
The ASUS is clocked a bit slower (800Mhz) than the saffire, but I get a decent 425Mhp/s at intensity 9 without the card breaking a sweat. That and I can still sell the card on the very active second hand market 6 months down the line without feeling bad.