I'd go for more RAM - unless you can find a GPGPU (aka general purpose GPU group) add on that shifts load to the GPU (a wish list item today - it could appear tomorrow (for Photoshop CS2 or 3) next month, next quarter or never).
I note that on a Intel QUAD core, 2GB machine with a 8800GTS card and oodles of RAIDed HARD drivers some PS 2 operations still take 30 secs to 2 minutes - I can't see you doing these operations on a lap top in under 2- 5 minutes unless you have alot of RAM and a lot of luck!
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