Stable overclock for XFX Double D 7970?

[PCCMaster]

So, I was messing around with AMD Catalyst the other day, and noticed under Performance" you could easily OC the graphics card. I'm running an XFX Double D 7970, pretty sure its the Black Edition. Catalyst says the card can clock to 1125 MHz, and the memory can clock to 1575 MHz. I was wondering if I ever decide to do this, what would be a safe, stable MHz that wouldn't burn the card out and not use too much power (I have a 650 Watt power supply) Thanks!
Link to my graphics card:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814150586

 

[pyr0_m4n]

As long as you don't mess with the voltage, the card will become unstable long before you cause any real damage to it. I got a 7970 that's 1125 and 1575 and its running in a mining rig and still going strong.