I'm considering purchasing a new imac. However, I'm concerned that the graphics card in the low-end 24" won't be fast enough for me to watch HD television via eyetv in fullscreen. Would buying a 20" be less taxing on the graphics card? While I've seen some benchmark reports that have the 24"/2.66 faster than the 20"/2.66, they don't take into account whether this is just because the 24" has 2gb more ram. Thanks in advance for any advice.