A friend gave me his Radeon HD 5850 but the fan is dead. What's a cheap/good fan to replace the stock cooling? Or should I just get a new 7850? If I can get a decent fan for $20 I'll fix it but if it's like $50 or more it isn't worth it to me. Never bought an aftermarket heatsink/fan for video cards before so thought I'd ask the wise ones here.