Working off of Fireball (av. dmg 35) as the base spell, and a max of 9th level spell slots...
Also assuming Enhance Spell modifies the *base* effect of the spell (which I think it does anways)...
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* Empower x3 = Average Damage 87.5 (range = 25-150)
* Maximized + Empowered = Average Damage 77.5 (range = 65-90)
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* Enhanced + Empowered = Average Damage 105 (range = 30-180)
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Now consider it after taking Improved Metamagic once....
* Empower x6 = Average Damage 140 (range = 40-240)
* Empower x4 + Maximize = Average Damage 130 (range = 80-180)
* Enhanced + Empowered x3 = Average Damage 175 (range = 50-300)
* Enhanced + Maximized + Empowered = Average Damage 155 (range = 130-180)
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Empower does seem at first glance much better than Maximize. But it all depends on how reliable you like your spells to be. Maximize drives the base damage up considerably in each case, which makes it *very* reliable versus Empower which is only better if you actually roll well on the damage dice.
In *ALL* cases where it was used, Enhance spell drives up the base/average/max damage. Thus it does it's job very well IMO.
Now back to the inital point of this thread, regarding Intensify Spell....
Yeah, basically, it's a waste. Now, my contention is that the problem lies with this "epic" feat rather than stacking up Empower. IMO, it's cost should be lowered to +5 levels or so.