Bradley's last three years:
18, 17, 11 = average of 15
Durazo last year:
As you can see, the A's get a player enter his baseball playing prime, replacing two players who are existing it, and adding at least 6 more win shares, which roughly translate to 2 more wins on paper. also, remember that's just his average over three previous years--really two years if including injuries in 2003 and 2005--and NOT projecting for growth, and assuming Coliseum is AS BAD a hitter's park as Dodgers Stadium. The 2 games aren't enough to catch the 2005 Angles, but it's a step in the right direction.
P.S. It is difficult for me to believe Ethier in 2006 would be getting much playing time with the A's in the first place. Even if he survives AAA, AND gets called up in the second half, AND perform like Swisher did last year, that would mean half of Nick's win share, which would be 12/2=6.