Be cautious with M Faulk. Steven Jackson is getting more and more carries and the changing of guard is very distinct. Unless you have Jackson I would stay away from this trade simply because of that.
Portis has struggled but he is still a top RB. Emmit is a good #3 RB which are hard to find.
I wouldn't do that trade. I would rather have three healthy starting RB's (assuming you can start three RB's...even if you can't I would still keep them) and have a week #2 WR, then have 1 healthy RB, 1 RB who is fixing to be replaced by Jackson, and two top WR's.
But that's just my opinion.