In that price bracket, I'd second the Parker 51. I'd buy one that has been restored. Richard Binder puts some nice pens up for sale on his site at the beginning of each month. In modern pens, I'd go with a Sailor Sapporo or 1911, or something from Pilot/Namiki such as the Vanishing point or Falcon. A Lamy 2000 in F nib would be a nice one too.