I have similar specs in my laptop. Only 2 gigs of ram though, and I have a quadro 140m in mine which are fairly comparable to the 8400m from what I've seen. It runs on medium well enough at just a notch below optimum resolution IIRC.
I'm not sure of the legality of something that you don't have to pay for, but you can find the beta at the usual torrent places if you want to check it out yourself.