Well, how much is the marine stereo? We can better tell you if it's worth it.
I know marine components are usually more expensive. I don't think it's going to do what you expect though. Marine electronics are normally designed for boats. That doesn't necessarily mean if you drowned it in water that it is still going to work. It just means they added protective coating to the circuit board, which reduces the chances of moisture getting on the PCB and causing things to short out, or corrode. In a boating environment since there is a lot of water around, water tends to collect on electronic components just due to the humidity. This is the type of moisture that marine stereos help protect against. So if your marine radio gets rained on, it can fail also. With Marine speakers, they put a protective coating on the cones, so moisture does not collect on the paper of the speaker cone and cause it to warp or eventually fall apart. The same with the material that surrounds the cone. Moisture then drying will eventually lead to dry rot.
In my opinion...it's not worth it for inside your vehicle. If your radio ever gets rained on, it's just best to turn it off.....and let it sit for a few days, so there is time for the water to evaporate before you decide to turn it on again. A hair dryer would help too.
You're better off having a soft top and when it starts to rain. Pull over, under the nearest shelter and buckle it shut. You won't have to get Marine Carpet and Marine upholstery that way also....and don't forget there's a lot of other electronics in your Jeep that you should be more concerned about other than your radio, if it starts raining