Here's a third vote for using sugar in baking and just calculating the amount you can have and controlling your portion accordingly.
Selkie, in all I have read, Splenda is derived from sugar. (Chemically treated yes, but still originates with sugar) It is one of the few "sugar subs" my body will tolerate. I can't use any aspartame or anything like that.
Stevia is natural, but in a recipe it is difficult to sub because of the volumes. Where you would use 1 cup of sugar you only need a wee bit of stevia for sweetness so it throws your batter out of whack. Its good for sweetening things like coffee or tea, but not so great for baking IMO.
BritMom, there are lots of things you can do to reduce your sugar intake. If you do all those small things (no sugar in coffee or tea, or on your cereal, sugarless gums etc) then you will have room for the occasional dessert made with real sugar. You can easily calculate how many grams of sugar you are getting. For example 1 cup of sugar in a batch of brownies that makes 15 brownies 225g/15 =15g per brownie.
Welcome to DC, where are you in Canada? I'm in Edmonton.