I don't use them myself but Rhythmbox or strawberry music player are close/closest to winamp I would say.
Quod libet could be worth a try. Its got lots of different ways you can sort thru your music. Perhaps a bit closer to foobar2000 than winamp.
Its been a long time since I used winamp but I faintly recall it had automixing. Mixxx DJ software works well for this and would be alright for a player too.