I've had very good luck with Sony Marine Stereos, plus any "good" aftermarket speakers have a good degree of water resistance built in. Specifically Marine speakers are typically overpriced bottom end stuff with white grills...
My TJ has Pioneer 6.5s in the speaker bar, with Pioneer 4x6s in the dash and the attached Sony Stereo. Its rained on it innumerable times, still sounds great.
~2005 Disco 3 "Moneypenny"
~2008 GTI TSI
~If you can read this, thank a teacher. If you are reading this in English, thank a Veteran.