I found that with rebate from 2 different manufacturer, you can almost buy 2 4850 cards equal to the price of 1 4890 card. The question is will 2 brand of 4850 card work in CF? The FAQ says yes, but anyone really tried it yet? Will 4850 CF always out perform single 4890? Anyone got any benchmark?
and if you want dual 4890's then wait for the X2 model, it will have a slight performance boost because there will be more bandwidth between the GPU's. (15GB/s vs about 5GB/s I guess with a CF connector)