Stoneweed:
I used an SM009 for 9 years, and I did everything from smoked cheese to Prime Rib in it. I have done 15 to 20 pound turkey in it. The bigger ones are a tight fit, and yes, they will properly cook a turkey (you may have to finish them in the oven if you want crispy skin). I bought extra grills and side racks, and a cold smoke shelf. I did the same thing that you are looking at doing. I bought the smallest Cookshack smoker because it was less money layed out for something I had never seen or used. About 2 years into having the SM009, I realized that I should have spent the extra for the bigger smoker. I finally hit the getting the bigger smoker wall last year. I looked at the SM025, and the SM045 (same footprint, just taller). I got the SM045. The problem is that all of the extra stuff I had bought that were SM009 spacific, did not fit the SM045. The cost of the SM009 extras would have more then covered the extra that an SM025 would have cost. Go with the SM025. This stuff is adicting, and in the end you will save money when you upgrade. By the way, I did 2 20 pound turkeys in the SM045. These would have also fit into the SM025.