First of all, why go for the stainless steel one? I have both, and find the alu one is bombproof as it is, is lighter, cheaper, and spreads the heat better for more even cooking. Despite being an amateur stovie (boys love playing with fire etc), the SATs are my go-to stove, and always keep at least one set in the car.
Re the folding cups, the small ones are a bit too small. However, you can get the bigger version (600ml), which are excellent. I got most of my SATs and large folding cups from Military Mart - no connection etc - and have always got good service and prices from them. I actually bought a number for Xmas pressies last year (great to keep in the boot for bad winters or just an impromptu brew-up etc).
Agree 100% with recommendations to keep burner and meths bottle separate from the interior of the set unless stored in good-quality ziplock bags - having to wash out the smell/taste of meths before use is a pain!
Don't forget that the windshield makes a very good woodburner as well (both ways up!). It turns a nice coppery colour after the first burn or two, and gets a bit softer, but after multiple burns (50+ as woodstove) still does the job with no further signs of deterioration.
I'm currently awaiting a larger but very light (M4) burner from Minibull Designs with a "bird-feeder" set-up to give me extended cooking times for the SAT (several hours potentially) - will post details as and when I get a chance to try it out..........