Time for a new battery?

[Kashew]

I had to jump my car today for the first time in years. I think it might be time to beef up my battery with a deep cycle one. I have an '05 X5 3.0i. It has a radar detector, Sirius radio, and three emergency lights(similar to this, but they're usually not on) attached to the 12V sockets. Unfortunately, these sockets are always on and unplugging everything just isn't something I'd like to do every time I turn the car off. I also live in Upstate NY, so it gets pretty cold here too. Because I'm a volunteer firefighter, having to jump my car is a real inconvenience for me.

I know nothing really about batteries except that a deep cycle can discharge much more of it's charge.

Would a deep cycle battery be a good investment?

If it would be, what type of deep cycle should I get?