Yeah, I bought the 660 to help a guy out mentioned earlier and Ryan's 32" bar and chain. Not CAD....really....just need to mill up some downed trees from Irma and my Stihl 446 (044/046 hybrid) is not going to be ready soon enough. Plus you know....660.
If lumber retention is not a factor a smaller bar than 36 can work. Just takes longer and since 36" bars are common enough there is no reason not to go that route. I only mention this because if you cannot find a saw and still need to get started on the trees, a 440/460 class saw with a 28 or 32 "could" work. How good are you at plunge cutting? Even with a 36" it is going to be relatively time consuming to buck or stump anything 50-70" in diameter.