nForce+Nvidia video card=cool?

there isn't really a way nVidia could make it work better
nForce chipsets are better than VIA chipsets, so you could see a CPU performance increase (it can overclock better, so if you OC you can see the performance boost) and if you move from single to dual channel RAM you could see the boost

the only nForce chip that benefits nVidia graphics cards is the nForce4 SLI, whihc only benefits them by providing 2 PCIE x16
but Intel's Tumwater, and their 955X chips are also fully capable...

nForce + GeForce won't equal better performance
it just gives you more nVidia products, and more nVidia drivers to install
BUT
i'm not saying VIA is going to be equal speed
but let's consider

VIA KT400A with a Radeon 9800 vs nForce2 Ultra 400 with a Radeon 9800
let's say the choice CPU is an AthlonXP 2700+
the nForce system will perform better due to dual channel RAM, and it will overclock higher
but it won't make the gfx faster

if the 9800 were replaced with a 5900 Ultra, the only performance difference would be from the different cards (a 9800 performs different in certain appliations from the 5900) but the chipset would not affect it