More is always better :)
Seriously, though, I analyzed all my dissertation data on a 667 MHz G4 Powerbook with no problems, running 3ddeconvolve on big (>1300 time points) datasets. They key I think is lots of RAM (I had 1GB), so you're not swapping stuff between RAM and your hard disk. I'm now using a 17" Powerbook (1.33 MHz, 1GB of RAM) and it is noticably faster. Video memory is not an issue for the basic analysis stuff but is for SUMA. Data always expands to fill the space available so get the biggest drive you can... AND have an adequate backup system!!!
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