Hi guys, I have an iMac 2009 27” i7 and my grafic card ati Radeon hd 4850 512mb is broken (vertical lines). The question is: where can I buy a new ati Radeon hd 4850 or ati Radeon hd 6970 2Gb for e normal price? On eBay I find only used cards for a lot of money….Thanks :)