So I need an outstanding MP3 player for running.

Necessities:

-Flash player so it doesn't skip

-512 MB sounds perfect for a few hours of music

-Compatible with a reliable arm band so it doesn't fall

-Waterproof, unless the arm band will protect it from the weather and sweat

-Runs on some type of user-replaceable battery -- I'm not paying $60 for the dealer to replace the battery for me

-Quick and easy to plug-in and add/change songs


Any help is greatly appreciated, thanks!