Mark, don't mess around with smaller pots. You'll just get frustrated, and frankly in most of the pots I've played with there's less than an ounce difference between 0.5 L size. Go for a 2L pot. You might consider the AGG 2Qt and caldera/ti tri combo. Boiling 1.5L might take a while, but in "normal" temps it won't be a big deal.
Will lows in the 20s be pretty typical for you? If so, an upright canister probably isn't a great option for you. More futzing about trying to keep it warm, and while yes there are tricks, I'm guessing you'd prefer to minimize fuss. The Windpro is about as low to non-existent fuss as you'll find if you go the canister route. Easy to use, stable, good in variable weather... but it is heavier than other options. The thing is, if it works better for you and your purposes, or just makes things a bit easier, it's one place it might make sense to carry literally a few ounces more.
The Windpro is a great "family" stove. I've also had great luck w/the cones... families have cooked over alcohol for years, but the Caldera's more efficient and much lighter than Trangia... probably worth a shot.