I do not believe either would play this game. The 8400 is low end of a 4 generation old card... 8000,9000,200,400 ... If you don't own it do not buy the 8400. I have found a good card for most things is the 9600gt or 240gt if you are going cheap and can still do most games.. Others will give you ATI suggestions I have just mostly dealt with Nvidia. The 9600gt can be found on ebay for around $40 I just looked.
Ok looked up the specs for low end
256 MB ATI HD2600 XT or better, 256 MB nVidia 7900 GS or better.
Ok understand these are the low end meaning low res and posibly not smooth gameplay.
512 MB ATI 4800 series or better, 512 MB nVidia 9800 series or better
I would pick in the recomended area the 9600 being min I would get and 9800gt or gtx being what you want but prob waaay out of prince range.. Well happy hunting