Dolittle, I could see your Computer example working as follows:

Product Kit: Computer
 Product: Screen (price 0)
   attribute: Screen Type
     option: No Screen
     option: 19 inch (+$250)
     option: 21 inch (+$400)
 Product: Video Card (price 0)
   attribute: Video Card Type
     option: No Video Card
     option: Video Card (+$100)

Not ideal, and like I said...I don't think attribute price adjustments are taken into account in product kits or displayed during checkout or maybe even saved at all, but I think it could work.