Silo2 (affordable) and Rhino (more $$) are for me the best modelling packages
Zbrush is fantastic for organic modelling but the learning curve is long (still learning version 3,1)
For all around package at your range price ,i suggest Carrara Pro 6  or Truespace 7,5 (if you like the interface  )
Better suggestion:try demos and see by yourself before buying