I don't think you need much.
I would get a remote therm. I use a Maverick and have been happy with it. Others differ in their opinion, but I haven't found a remote model that is perfect yet.
I would get some heavy rubber gloves if you have to pull meat right when it's finished cooking. I got mine at Lowe's for about $12 and they work great.
Pick up one of their generic grill covers while you're there for about $10 for the smoker and you'll be happy.
Go to a restaurant supply store and get a few heavy duty half size sheet pans. About $5 each. Makes getting meat into and out of the smoker much easier. Buy a couple of extra because your wife will take at least two to bake on and wonder where they have been all her life.
You can punch holes in a disposable aluminium pan for the poppers, but the pepper holders are nice and I finally broke down and bought one. Check Cabala's as they have them on sale from time to time, but they seem to be the same quality as CS's. Get some disposable half pans from Sam's Or Costco though because they make pulling meat and storing it much easier, and then you toss them so cleanup is easier too.
CS's rubs and sauces are extremely good in my opinion. On butts I use a "secret" rub that is made from garlic salt and cayenne pepper. On brisket, I go crazy and add black pepper. Don't tell anyone.
Lastly, if you plan to cook a lot, both in frequency and amounts, buy a nice stand. You might be able to find something used at a good restaurant supply store, but even new, a 2'x3' stainless stand shouldn't cost more than about $150 max. Here's what I'm talking about:
http://www.webstaurantstore.co...-legs/600T2436G.html Cut, or have someone cut, a 4-5" hole under where the drip hole will be, and then put a 5 gallon bucket on the lower shelf to catch drippings. It takes the worry away from forgetting the smaller included drip pan and then having a mess one morning, that is assuming you don't forget to empty the 5 gallon bucket.