Minty - you are right about good closers moving to new teams and closing. K-Rod might be an example recently. however, more or less the rule on closers is they become pretty cost / length of contract prohibitive to sane GMs as they get close to free agency. K-Rod and who signed him would be a good example. The true elite, like Wagner, are in a different class. Maybe Storen is in that class, but it is too early to say, and the burn out rate is pretty high.
I agree Storen shows some signs of being a rare one who has the head and the arm, and has quite a bit of value in trade. I don't view it as ludicrous that he brings back a player who is a good starting CF whose only weakness is power. I'd swallow hard, but probably would do it if I were satisfied with Span's meds.