In addition to what Loren said..

I suggest getting your options through http://www.subaruparts.com/. You will save big time.on the security system and arm rest extention. Personally, I'd not get the arm rest extension if you plan on ever getting a short-shifter or like to do aggressive shifting because it might get in the way... sit in both and see what you like.

In the Subaru community, it's generally agreed upon that the OEM gauge pack is junk. I'd save your money and get an aftermarket one. You really don't need those guages until you start modifying your car anyway, and what better time to get some that you can actually read?

Finally, I'd recommend going to www.nasioc.com and seeing the "Regional Forums" and meet people from your area. They are generally very nice. You'll meet people that will work on your car with you and who have a lot of experience. I gotten thousands of dollars in labor done to my car for free from local club members. They've also recommended local dealerships, vendors and shops. Most clubs have weekly meets too so you can see all those cool mods in person.

Oh yeah, welcome to the club.