H.264 encoder with CLEAR options for specifying minimum & maximum video bitrate?
From http://ffmpeg.org/ffmpeg.html , you can do this in CLI.. not sure about GUI.


  ‘-maxrate bitrate’
  
  Set max video bitrate (in bit/s). Requires -bufsize to be set. 
  
  ‘-minrate bitrate’
  
  Set min video bitrate (in bit/s). Most useful in setting up a CBR encode   
  
  
    Eg: "ffmpeg -i myfile.avi -b:v 4000k -minrate 4000k -maxrate 4000k -bufsize 1835k out.m2v"