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it's really hard to say without knowing what else is bringing your score down, but I would guess 20-30 points for each util bracket you get under. so if you went back and paid another 800-900 on the mastercard I think you would see maybe another jump that might put you in your range.
oh if all you have is a car loan and personal loan... you need some credit cards!
Couple Visa or Mastercards and 1 store card should give you a great score boost