rheinmetal,
 
you can't fry one of these cards unless you allow it overheat significantly or if you disable the over current protection when you use furmark, occt, kombustor, etc to stress test.
 
make sure you update the bios uses the fan unlocker update posted in these forums.
 
start by overclocking your core clock by 25 mhz or so. this will change your shader clock automatically by 50 mhz. the 580 SCs seems to have no problem hitting 900 mhz if the default voltage is around 1.082v. if the card fails at a certain OC and it's staying really cool, bump up the voltage 0.010v or so until it's stable. both of my 580sc can do 975mhz in SLI or more individually at their max voltage of 1.150v. you may not see results that high but it these cards can do it if you got great chips.
 
once you've maxed out the card core/shader OC, set your gaming OC to about 25 mhz less to ensure it's rock solid. then go back and start bumping up the mem clock until it is no longer stable, find the max OC, then back down about 25 mhz or so.
 
I also run my cards at 100% fan anytime they're above 50*C using a custom fan profile. some may think that's extreme but i prefer to keep them as cool as possible when folding especially but in game too since i wear headphones. the result of really cool cards means less voltage is needed to sustain higher OCs.
 
for my cards, if the game is a DX9 game I run them at 925 mhz at default voltages of 1.082v with no issues. for dx10/11 games, i have to bump it up to 1.110v to get rid of all artifacts in game. my temps never exceed 65*C under any conditions.
 
good luck, and make sure your PSU is rock solid stable as these puppies love some clean power! right now both cards are at 100% usage and the CPU is mostly idle. i'm drawing 600W from the wall and at 85% efficiency that's 510W DC. at 100% utilization of CPUs and cards, that jumps to 850W AC or 722W DC. i hope that gives you a solid frame of reference to work from.
 
as far as applications go, oc scanner, precision, and eleet are nice, but i prefer actual synthetic benchmarks like heaven or 3dmark11, 3dmark vantage, or in game benches like just cause 2, crysis, etc. instead of precision, i typically use afterburner 2.1 and set custom fan profiles and, unlike precision, you can adjust voltages in afterburner as well.