Need advice for overclocking GPU

[IllogicalGlory]

XFX Radeon 7870 2GB - runs at 75 degrees C when using Unigine benchmark
HIS Radeon 7850 2GB - runs at 65 or so
Corsair TX750 PSU
i5 3750k (@4.2Ghz) - temperature barely changed from stock settings
Sandisk 32GB SSD

All cooling items are stock/generic

What would be an acceptable level to OC to and would I need more gear?

 

[futurefields]

What resolution are you running?

At 1080p I wouldn't overclock, you are already getting more than enough performance with what is essentially dual-7850's. (i believe your 7870 reverts to a 7850 if you crossfire it with a 7850)...

But if you really want to, then just boost both your cards by 100mhz and run Unigine Heaven 4.0 for about an hour straight and see what happens. If everything looks good then keep it, if you want more, then go for another 100mhz and run Unigine Heaven 4.0 some more.

These cards have thermal overload protection and the OC apps are designed to keep you within a range that you can't physically damage the cards.

 

[aarontpx]

Every card will overclock differently. I am sure you can find some overclock guides for those cards if you looked around.