8400 GS vs 8500 GT

Both of those cards are just one step up from onboard graphics... if by "gaming" you mean "playing WoW" either should do ok... but anything remotely modern will punish those cards.

You've been warned... now go buy one 'em anyway.
 
According to this nice chart on the back of an 8600GT box I just happen to have lying around. The 8500 is about 7 times better than Intel Integrated Graphics, which is pretty much the worst out there. The 8400 is not even listed. With the price gap between the 8600 and the 8500, buy an 8600.
 

Which Intel GPU were they testing? If it's the GMA 900/950 series... sure... if it's the X3100... hah... I think Nvidia is being dishonest.
 
The 8400GS is for people who like me who don't game but hate integrated graphics. I hate integrated graphics because I refuse to give up system RAM just to run my monitor, plus I do some light gaming now and then. Overall, cleeve said it best far as gaming goes.
 
@rodney_ws : I would have to believe that it would be the 9 series Intel Integrated graphics. There are not too many OEM machines with the X3100. At least they don't call it Intel Extreme Graphics any more.
 
I have read of some crazy overclocks on the 8600Gt with air. Don't know how easy mounting the block on the GPU will be though. It is hard to find anything beyond stock for the 8600.