Hi, I'm interested in getting one of the new 21.5'' iMacs and am stuck between the base model with 9400m or the 4750 version. Primarily, my concerns are about the 9400m's ability to handle HD video editing, has anyone used this graphics chip for HD? How did it perform? My budget really doesn't stretch to the quad core models, so it's between these two. Thanks in advance for any advice.