Well, I personally use iZotope Ozone for Winamp to warm up my wave/mp3 files, You can also use the VST version, although that one costs much more, it has a lot more features.
You can download a limited version of the Ozone plugin for Winamp at: http://www.winamp.com/plugins/details.php?id=79374

To render your wave and/or mp3 files, just install the plugin and change the output to Nullsoft Disk Writer in the Configuration window of Winamp.

The full version of the Ozone plugin for Winamp costs $29, the more elaborate VST version costs $249.
http://www.izotope.com

Greetz ,
Marcel

PS: If you want a better mp3 decoder for Winamp try the MAD plugin: http://www.mars.org/home/rob/proj/mpeg/mad-plugin/