Your best bet is to pick up a cheap vid. card. Very few Full ATX motherboards have integrated graphics, especially nForce. Also, by getting an nVidia chipset, you will not see much greater performance versus integrated Intel graphics. They both suck, it's integrated graphics, but, just about anything should work with older emulators (GBA, PS1, n64, NES, etc...). But, if you buy a nicer board with 2 pci-e x16 with no integrated, get a cheap GTS 8400 or something (Like, $20 on eBay) you will be FAR further ahead without spending anything more than but you think you need to be looking for.
Also, It appears the mGPU you desire is only avaliable on mATX motherboards. (From nVidia site) and also, the chipset only supports one PCI-Express x16 card. (i.e. won't work with 2 at x8.). Not to burst your bubble but it doesn't appear to be possible. If you find a board for it, post a link but I highly doubt they are around. The chipset dosen't seem to support it thus, a board couldn't do such. That is what the "PCI Express Configuration 1x16 + 4x1" means on the specifications of the chipset nVidia posts.http://www.nvidia.com/object/main_mobo_gpus.html