I had assumed that doing graphic edits would require a good graphic card.....hhhmmm
All the hard work is done with the processor and internal memory (or swapping to disk if insufficient memory), even the most basic graphic card is capable of slapping the resultant output on the screen in a split second.
Quality of output (colours, contrast) is very nearly identical for all cards unless you are using very fast raster speeds on a CRT, its the screen that makes the 99.9% of the visual quality.
I guess if you are doing serious quality graphic editing then you will be calibrating the screen, the only thing you can't calibrate out is again very fast raster speeds on CRTs (due to limited frequency bandwidth of the CRT and the D-A converter on the graphics board.
As you are looking at a laptop, you will be stuck with a LCD screen, I would be looking more at the quality of the screen not how "flashy" the graphics processor is.
Many laptops don't have changeable graphics cards in them anyway - this is a big moan from the Gaming community where they want high speed animation by having the latest graphics processor with loads of hardware acceleration.
I can't comment on quality of LCD displays, IMHO they are all rubbish compared to a good quality CRT.
I don't know how purist you are, but normally your eyes and brain adapts to whatever you use, as long as the resolution is high enough for the detail you want, I would not particularly worry about the screen either - just main processor power with quite a bit of memory so changes you make happen quicker. I was waiting 50 seconds a time yesterday with some image processing I was doing on my old dilapidated laptop.