I have an 08 wrangler and having a waterproof HU isn't necessary at all. I've had it downpour inside of it with the top completely off and it didn't hurt anything. If you plan on going double DIN with a screen I'd be careful but if not than anything that fits your needs will be fine.
If your getting an 07-09 don't bother trying to find a wiring harness.....unfortunately you have to hard wire it which is tricky to get all the speakers right but it works just fine.
If you need any other help with your jeep let me know.