So i am currently running 2 sapphire 4850's 512m in crossfire. I was wondering if it would be a worthwhile upgrade to go with a single 5850 or 5870? I would likely later crossfire whatever i get now as well, but for the moment can only afford one card. Any insights? Or should i stay with my current set up until i can afford to crossfire whichever i decide on later? Oh, and which is the better buy? 5850 or 5870? im leaning toward the 5850's myself, they seem to be more dependable from the reviews i have read. Thanks in advance for any advice rendered!!