I don't know about winamp but i use acoustica, which isn't free but it is easy to use and can convert mp3 to mp3 (decrease quality) and can handle bundles.
the thing about dbpoweramp is that it encodes mp3 in a really slow speed (4x realtime i think) which takes a lot of time. i know it can convert mp3s to mp3s but i don't want to install it just for that, as it can rip cds. i prefen audiograbber and cdex to rip cds. anyway, i will try cool edit pro 2 'cause i think it can save convert mp3s the way i like it.