How about this:
Feats
Small: Power Attack
Medium: Cleave, Power Attack
Large: Cleave, Combat Reflexes, Power Attack
Huge: Alertness, Cleave, Combat Reflexes, Iron Will, Power Attack
Greater: Alertness, Cleave, Combat Reflexes, Lightning Reflexes, Iron Will, Power Attack, Weapon Focus (slam)
Elder: Alertness, Cleave, Combat Reflexes, Great Cleave, Improved Bull Rush, Iron Will, Lightning Reflexes, Power Attack, Weapon Focus (slam)
Monolith: Alertness, Awesome Blow, Cleave, Combat Reflexes, Great Cleave, Improved Initiative, Improved Natural Attack (slam), Improved Bull Rush, Iron Will, Lightning Reflexes, Power Attack, Snatch, Weapon Focus (slam)
Skills
Small: Listen +2, Spot +2
Medium: Listen +3, Spot +3
Large: Listen +4, Spot +5
Huge: Listen +9, Spot +10
Greater: Listen +12, Spot +13
Elder: Listen +15, Spot +16
Monolith: Listen +23, Spot +24