Is Powercolor a reliable GPU brand?

Depends on the specific GPU.


Well, it will have a two year warranty from powercolor: http://www.powercolor.com/us/support_warranty.asp

I've used one powercolor GPU previously and it was fine. I cannot find any specific reviews focusing on the reliability of the particular GPU though.

powercolor is a great manufacturer. They build at the same level as HIS and Sapphire.  They've been the official maker of the manufacturer for the 7990.  They're in a way in house tuners because of their contracts together.