Hello everyone, I was wondering which of the two new 21.5 iMacs I should buy. 500GB HD is enough for what I am doing, but I am worried about the graphics card. Can the 9400M be replaced? or the only model which has upgradeable graphics card is the one with ATI 4670? Also, are there any benchmarks around about these cards? Is 4670 a better card than the 9600M GT found on Macbook pro's ? Thanks in advance.