Well, depends on how you want to overclock it. I have the powercolor 7870 Myst, and I did expirment with overclocking a bit with litecoin mining. I can say this, the card is LOUD when overclocked, but mine only has one fan. I think it should overclock okay, but not sure.
You can get a Sapphire card for cheaper than the gigabyte eventually I think though.
LOL! So true on the Myst! That card is actually a Boeing engine in disguise!