Spicy Watermelon Gazpacho

Name: Spicy Watermelon Gazpacho
Ingredients: 1 Teaspoon pasilla chili powder; 1 Teaspoon New Mexico chili powder; 1 Teaspoon pimentón (Spanish smoked paprika); 1/2 Cup sugar; 1/2 Cup water; One 3 1/2-pound seedless watermelon, peeled and cut into chunks; 1/2 red onion, chopped finely; 1 red bell pepper, seeded, de-ribbed, and chopped finely; 1 yellow bell pepper, seeded, de-ribbed, and chopped finely; 1/4 Cup finely chopped fresh cilantro, plus sprigs for garnish; 2-3 limes, plus 1 slice for garnish; Salt and freshly ground pepper, to taste; 1 ripe avocado, peeled, pitted, and sliced, for garnish