Hypersmurf
Moderatarrrrh...
You know, until I saw this thread, I thought Power Attack and the modifier was per attack.
Be warned - that House Rule gives Power Attack quite a boost.
One of the major disadvantages of PA is that it reduces the likelihood that your non-primary iterative attacks will hit even more than normal.
eg: Fighter with three iterative attacks at +19, +14, +9 attacks a creature with AC20.
Normally he can expect to hit with his primary attack (almost)guaranteed, 75% chance of hitting with his second, 50% with his third.
If he puts 10 points of Power Attack in, those odds become 50%, 25%, (almost) 0%. (Plus his chance of hitting with an AoO drops to 50%.)
But if he can choose his Power Attack number for each attack, he can PA for 10, 5, and 0 respectively, giving himself a 50% chance of hitting with each of his three attacks, but still getting extra damage with the first two... and he can bump his AoO attack back up to a guaranteed hit.
The House Rule removes a large portion of the "tradeoff" aspect of Power Attack.
-Hyp.