Add celery, onion, and garlic to a blender or food processor and pulse into small pieces.
In a large stock pot over medium heat, melt butter. Add pulsed veggies to the pot and cook over medium heat for 7-10 minutes or until fragrant.
Add tomatoes, oregano, broth, and basil to pot; bring to boil, stirring occasionally. Cover, reduce heat to medium-low, and simmer for 15 minutes, stirring occasionally.
Carefully pour 1 cup of hot soup into blender and add cubed cream cheese. Blend on high until smooth.
Stir cream cheese mixture into soup, add sugar or agave, add salt and pepper to taste. If you want a completely smooth soup you can puree all of it in the blender.