If you want a Core Clock above 1150Mhz, will have to bump up the voltage a bit more.
This is what I'm running on my Sapphire HD7870 Ghz.http://i1146.photobucket.com/albums/o537/Manofchalk/Untitledpictureghv_zps7c395910.png
I could probably push it further, but its already a decent overclock and its somewhat loud under load.
Very nice manofchalk! This is the OC i got to the other day... It did seem stable at much higher settings but after a few hours of gaming it started to crash.
This is the sweet stop i found.
This is my results in FurMark on the benchmark preset 1080p (GPU stress test tool).
These temps are high, but they only get that high in stress testing.
The temp only gets to around 50c while playing bf3 for a few hours.
This is results from running the same test on my GPU with stock settings.