I think it depends on whether or not you have the option to start a third RB in a flex position or not. This trade would be tough to me. First of all, even though Chad Johnson is not having as great a year as usual with Palmer at the helm, I expect he will start putting up even better number. Marty Booker I dont really care for at all. Taylor is not a bad running back but has been inconsistent this year. Chambers is on a Miami team that can barely move the ball and his numbers should be way down. Getting rid of Booker is a good idea but I would personally keep Chad Johnson especially when looking at your receivers you'd have left.
I'm not a fan of Chambers or Booker this season. I think Chad Johnson will come around at some point. Fred Taylor is a bit of an enigma to me... I can't quite figure him out, although I think last season may have been his last hurrah. I'd stick with what you have right now and look to find that waiver wire RB to replace Booker.
Booker is garbage this year. I'd rather have Ike Hilliard, Antonio Bryant, Kevin Johnson, or anyone in that value range. I drop Booker ad pick up someone else in lieu of making that trade.