Amplifiers:Software

Are there any software packages out there that are used, specifically, for amplifier design? Or are they all used simply for Electronics:Software?

PSUd 2 is specifically intended for power supply design for tube amplifiers.
http://www.duncanamps.com/psud2/
It's Free
It enables you to predict certain characteristics, e.g. output voltage, of tube amplifier PSUs, given details of topology and components.

Please enter the following info for the package:

• Name
  
• URL to main site
  
• License (Free, Commercial or Lite version and Pro version)
  
• What it does