Got enough video memory for Aero?

[ulrich.von.lich]

According to Microsoft:

64MB for 1024*768 only
128MB for any resolution up to 1920*1200
512MB for greater resolutions

But what if I want to have dual monitors?? How much video memory will be enough to ensure that Aero runs on both monitors?? (two monitors of 1920*1200 for instance)

The answer would be: 256MB (128MB for each) or 512MB (2*1920*1200 is greater than 1920*1200)??

I'm assuming the amount of video memory mentioned here comprises both on board memory and shared memory.

And can anyone tell me, why graphic memory is the only thing that matters? A 128MB 8600GT is more powerful than a 256MB X1300