In a small bowl, combine chili powder, cumin, 1/2 tsp. sugar, 1/4 tsp. salt and the cayenne; set aside. Heat 1 tbsp. olive oil in large skillet over medium heat. Add pecans and heat, stirring occasionally, until crisp about 5 minutes. Stir in spice mixture and mix to evenly coat pecans. Cook 2 minutes. Turn pecans out onto paper towel to cool. (Nuts can be prepared several days ahead and kept in an airtight container.)
Heat grill to medium-low heat. Cut peaches lengthwise to make thick wedges. Coat grill rack with vegetable oil cooking spray. Grill peach wedges on one side 3 - 5 minutes or just until lightly browned and a bit tender. Remove to large plate.
To serve, toss the salad greens with vinegar, the remaining 3 tbsp. oil, 1/2 tsp. sugar and 1/4 tsp. salt. Divide greens among serving plates; top each salad with several peach wedges. Divide spiced pecans and the chevre among salads and serve immediately.