Pinchy's right, you can put most any deck in there of your brand preference. Shop around though definitely, surprisingly, even local specialty audio shops carry the same products you can see online with cheaper price tags. Also, do your homework. Check out the various features of the head units and see which ones you can make use of and which you won't. For instance, there's no use in buying a head with a built in xm tuner if you never intend to use it. Stuff like that. It'll save you from wanting to drop a rather good chunk of change down the road. I've got an alpine head unit and am fairly satisfied with it!
OH and just to re-iterate what pinchy said. BUY THE HARNESS! :grin: It's the easiest route both for install and for if you want to change units down the road.