1. In a large saucepan, heat 4 tablespoons of the oil over moderately low heat. Add the onion, bell pepper, garlic, chopped basil, and oregano. Cook, stirring occasionally, until the onion is golden, about 10 minutes. Add the canned and fresh tomatoes, the broth, salt, and sugar; bring to a simmer. Reduce the heat to low. Simmer, uncovered, until thick, about 30 minutes.
2. Meanwhile, heat the oven to 350°. Put the bread on a baking sheet and toast in the oven until crisp, about 25 minutes. Remove. Add the bread and the pepper to the sauce and bring to a simmer. Cook, stirring gently, until the bread absorbs all the liquid, about 5 minutes.
3. Discard any mussels that have broken shells or that don't clamp shut when tapped. Put the wine, mussels, and 1 tablespoon of the oil in a large stainless-steel saucepan. Cover and bring to a boil over high heat. Cook, shaking the pot occasionally, just until the mussels open, about 3 minutes. Discard any mussels that do not open. Mound the bread soup in shallow bowls and surround with the mussels and broth, leaving any grit in the pan. Drizzle with the remaining 1 tablespoon oil and sprinkle with the sliced basil.
Wine Recommendation: With such a regional dish, the wine almost has to come from Tuscany, too. Try a Rosso di Montalcino, Brunello's lighter, less costly cousin.