Graphics cards is a bit more dificult.
The PC World web site does not list individual graphics cards, only the amount of memory on them.
I would say 256Mb of graphis memory is plenty for "general" computing (could probably get by on 128Mb).
Unless you plan to play games then you probably dont need to worry too much about graphics cards.
Gamers can pay up to �250 for JUST the graphics card, but for those of use doing basic "office" work probably any graphics card will do.