Have you taste tested Stevia. Many users detect a bitter/metallic after taste, I don't use it because I can detect that after taste.
If you are going with a sugar substitute the only thing you need to do is to substitute is to make a sauce you really liked, and substitute the artificial sweetener. If you use stevia or many of the other substitutes out there, you may find you will need to add arrowroot, or cornstarch, or Xanthan gum to thicken up the sauce. Just make small test batches until you know you like the finished product.
I wouldn't buy any of the commercial brands unless a friend recommended them. Many are pretty nasty tasting.

If you use the phrase "sugar free" in your search, read the recipes, labels or contents closely, many use "sugar free" for products that have no added additional sugar, but could still be very high in carbohydrates.
To further cut down on carbohydrates, you may want to explore mustard base and vinegar based sauces.
One thing I forgot to mention. If you don't go with stevia, make sure the substitute you pick is heat tolerant.