Which of these players would upgrade my team most? ?

It depends on your scoring system and how many players you play each week at each position. I would forget about Gates if you're in a standard Yahoo scoring system. There's not a big enough difference for that to make a difference unless you thought you might lose Gonzalez next week this way. I'd be looking at Westbrook, Turner, Johnson and Moss out of this group. None of these guys have been totally consistent week in and week out. One big advantage with Westbrook is his versatility since he's an integral part of both the running and ping game for the Eagles. The potential down side is that the Eagles play defenses in the top 8 against the run in 4 of the next 5 weeks - the only exception is week 15 against the Browns. Turner gets 4 run defenses in the 12 - 19 range plus the #2 Vikings. The problem is that the toughest two defenses are weeks 15 and 16. Johnson plays three weak run defenses including the #32 Lions, but also has the Jets and Pittsburgh. After Seattle in week 12, Moss doesn't have a particularly easy schedule and the Redskin offense really hasn't done much in several weeks. Although Westbrook would seem to be the obvious choice, I think I'd take Turner.