First off, go to http://www.subaru.com
and build your own car the way you want it. Print up the "window sticker" they offer and bring it with when you go to buy a car. That'll help save on some stuff.
Secondly, the armrest... Some people say it gets in the way, personally I love it and it never gets in my way. It took me about an hour to get used to it once I had it installed (had to order it so I drove without for a week), but I love it now.
The guage pack... well I didn't get that one but I don't think it is worth it, personally.