Don't think any of those players would have made a difference to the result of the series. Gilchrist had been well and truly found out by the end of his career, even a half fit Flintoff would have walked all over him. Hayden may have been useful with England not playing Hoggard these days and Anderson's continual attempts to bowl away swingers at left handers instead of inswingers, but his record in England is poor and I doubt it would have mattered much. Symonds is the same as Hayden, although I suppose his part time bowling may have helped him out.
Nonetheless, one batsman can rarely make a huge difference to a series result unless he has the series of his life, whereas one good bowler can make a huge difference. Therefore, Australia missed Lee more than any of those guys.
Tendulkar = the most overated player EVER!!
Beckham = the most overated footballer EVER!!
Vassell = the biggest disgrace since rikki clarke!!