Seed and finely chop 1 tomato; reserve. Coarsely chop remaining 5 tomatoes. Combine 1/2 tomatoes, 3/4 cup tomato juice and garlic in a blender; process until smooth. Repeat with remaining coarsely chopped tomatoes and 3/4 cup tomato juice.
Whisk lime juice, oil, vinegar, salt, sugar and oregano into tomato mixture. Stir in reserved finely chopped tomato, green onions, celery, cucumber and jalapenos. Refrigerate soup, covered, at least 4 - 24 hours to blend flavors.
When ready to serve, stir soup will; ladle into chilled bowls. Top with croutons, avocado chunks, bell pepper, cilantro and sour cream