Wow. Just having Arod, Pujols, Vlad, and Prior all on the same team is an amazing feat in itself, but you have a great cast to go with them and that's no understatement. If you lose this league, I would just have to see the team that beats you.
I wouldn't touch Walker, he's just too risky. With that monster team, you could just play it safe with Polanco or Ibanez. Either one wouldn't be too bad.