the 946gz info is wrong.
intel's page for the 946gz / pl both say that it is 800bus max. that was the pre launch spec apparently because the day it came out intel themselves released boards that supported the 1066 bus. i know i own one. i have an intel d946gzis which is 1066 bus. there is an entire line of acer computers that supports it too.
apprarently intel then designed another chipset line the 945gz (notice the 5) that is 800 bus and also is in a lot of core 2 based boards (i also have one of these). these 2 types of boards are definitely value boards, but they are just as fast as basically anything else for intel , just they only have 2 ram lots, no raid , 4 sata ... no big deal anyway.
i think the main difference between the 946/945gz and the 945g is that they were supposedly fabbed on 90nm fabs instead of 130nm so they use less power. the 946gz apparently also has a gma3000 igp like the q965 (i guess the main difference between those 2, is the q965 has ich8, vpro, more ram slots)