Voxengo Radio is not "radio/amp sim". On the contrary, it does not touch your incoming audio but gently adds some very nasty artifacts to it, like ones that you can hear when trying to fine tune your FM receiver. They seem to depend on amplitude of incoming signal. And they sound so gorgeous!:
Very beautiful, natural and unusual type of subtle HF sound coloration.
Easy to use, well-thought filtering and dry signal knobs.
Free and really unique. Hard to come by, but worth it.