Need some help with laptop media storage solution

I have a Dell e1505. I use it as a desktop replacement. Its hard drive is only about 75gb and my music library is 120gb+. Also, my goal is to be able to play my music on my stereo.

I've thought about many options but here is currently the most appealing one to me, problem is I'm not sure if it will really work or how to go about best choosing a product that will maximize performance, so here it is.

My thought is to get an external, portable hard drive of at least 160gb. I will need one that is powered by the laptop itself. As ghetto as it may seem I am gonna use some velcro to attach it to the top of my laptop. This laptop never leaves my house so I am not worried about appearance or anything. At that point I will get an apple airport device to stream my itunes library to my stereo.

So will this work or have I oversimplified the process here? Anything I should be looking for in a hard drive for the way I am planning on using it? I'm pretty good at diy'ing with pc's but when it comes to knowing what to look for in a hard drive for this particulat application I am fairly lost. All I can determine is that I want a 2.5" drive with 160gb+. Not sure if usb2.0, firewire 1394 or some other way is best to connect it.

Thanks for any help.