Definitely Arbuckle, plus the picks were both high and plentiful, and Wade didn't trade anyone away.
It also didn't completely end after that core group, they just started trading the last remaining bunch of good prospects, with good reason. Happ, Carrasco, D'arnaud, Vilar. Brown was the last of that generation (it could have been him instead of Taylor at the time of the Halladay trade).
Gillick struck gold with his Werth connection and I'm not sure the Phillies really knew what they had in Victorino, they just got lucky another team did not (in that he was released from the Rule 5 stipulation).
The Gillick/Amaro brain trust also turned to be pretty bad at acquiring other teams' prospects. From Lee to Hamels.