What lens I need to capture on stage performance

AAC

Quite offen I need to shot on stage performance for business record and sometimes flash is not allowed  I'm able to walk around the performance venue for good shooting angles but on stage lighting keep changing for differnt effect.  Need to zoom-in for performers and zoom-out for whole stage.  Under such critical situation, what lens should I consider for D-SLR ? The bigger aperture the better ? and what's the price range to consider ?  In SUCCESS's GM show, I saw people used big tele-lens capatured picture from front stage, is it necessary ?  

[ 本帖最後由 AAC 於 2007-12-14 10:45 編輯 ]

AAC

I'm Nikon useer.  Should I go for Nikon or Sigma, Tamroon ...etc are fine too ?
I don't want to take chance after paying $1000+ and find it doesn't get my job done. Where can I rent or test lens suggested by you guys ?