I use a combination of Davincci syrups (liquid splenda sweetened) and stevia extract. This means no carbs or fillers. However since the DaVincci is a liquid other liquid in the recipe must be reduced to compendate. Also for some recipes that rely on sugar or fillers for texture something bulkier will be needed. For items such as beverages, cheesecakes, and other desserts that don't need the sugar texture, these two sweetners are amazing together.

Have you tried tempering the chocolate to see if there is a better taste. Maybe mix in a little cream as well?