Personally, I wouldn't get many of them at all. You can get, and install, most of them on your own and save a lot of money.
I have the upgraded security and I think the dealer wanted 400-500 for it and I got everything I needed, plug-and-play, online for about 150. I think most of them come with the instructions too so it makes it even easier to install.
you can get them cheaper, but i'd recommend armrest extension, auto dimming mirror, short throw (although i've never felt an aftermarket short throw) and security upgrade. my insurance agency recognized the security and i got an insurance break on that.