For ATI/Radeon cards I only use Sapphire. The have been very good for me over the years infact the first Sapphire card I ever got (a 3850 AGP) is still running in a rig to this day. Over the years I have had a 3850 4850 5850 6950 and a 7950 all working great.
O i mean its kinda late for me to ask but is Diamond even a good brand i had a problem with my last one. sent it back awaiting my new one, but i am just not sure; i was using a VisionTeK 4670
i am just seeing how much of a price difference the two have. I have no idea if its worth going for 260$ for the 7870 or paying 112$ for to 7770