Definately checkout http://www.arturia.com/ and try some of the Classic Synth VST plugins because I think they have the fat warmth you are looking for. You can download 15 day demos from http://www.arturia.com/evolution/en/downloads/demos.html
And I see you can get them all in a bundle in Dream Studio which looks like good value for 10 classic synths. Arturia have a great reputation for their VSTi synth emulators. And you can bet that almost all those warm fat pad sounds you like were made with analog synths. And often the pads you hear in New Age compositions the analog pads may be overlayed with digital sounds such as strings, flutes etc to create a more complex pad. But the analog pad always carries the warmth and body of the sound. So be prepared to sometimes use more than one synth engine to build the sound texture.


Also watch this Youtube featuring the Top 10 Free Soft Synths. There are some nice fat pads in this demo. By the way have you tried Crystal http://www.greenoak.com/crystal/dwnld.html ? It is an old one but free.