I took some advice I had read concerning how long term noise can actually be stressful and cause us to be physically tired without even exerting energy.Popwar: Rather than threadjack, I'll start my own thread, and I'd like to hear your experience.
To OP, I wouldn't worry about the sub damaging your ears. I've heard (though haven't researched) that distortion is harder on your eardrums than volume alone, so I'd avoid overdriving your system to a point where it sounds distorted. My ears hurt more after a few hours driving on the highway in my POS work pickup (underpowered, poorly insulated, cheapest pickup my employer could possibly get) than after a few hours driving with my stereo up.
When I used to put on a lot of miles, I decided to test the theory. Simply putting some chunks of cotton ball in my ear to knock down road noise actually made a noticeable difference.
The good thing about the cotton was I could adjust it to get the best compromise between cutting down road noise and cutting out “all” sound.
Give it a try the next time you have to put in some windshield time. You might be surprised at what it can do for you.