In France, buying a 6800 directly from FSC would cost a whooping 590€ (its part # is UWL:80-1P7100-C1 (VGA BOARD ASSY NV42M HYNIX 256MB REV.C1))! That is two-thirds of the price of the whole laptop nowadays ... The 7600 and 7900 are priced at 285 and 385€ respectively, shipping included; however, their installation does require a slight modification of the heatsink with a Dremel kind of tool -- There is one memory component that is a bit too tall according to what I read.
I know of two people who recently purchased two such cards to replace their busted 6800. They seem to work without mishap thus far; anyway, if you were to get one too, be sure to keep intact the thermal pads of your 6800 ... FSC don't sell them and it seems to be hard to find as efficient pads as theirs.