Another point on this is that you should discuss with your DM (if you are not the DM) about increasing the total by 50% as opposed to each individual die.
For the psionic Empower Power feat, it states:
"multiply 1-1/2 times the damage total of the augmented power".
I suggest doing this for spells as well as psionics.
Although doing it this way does slightly increase the total result, it is a LOT faster to calculate the answer.
For example:
a 12D6 Empowered Cone of Cold (empowering every die) does 60 points of damage on average.
a 12D6 Empowered Cone of Cold (empowering the total) does 63 points of damage on average.
But, calculating the extra damage per die for 12D6 might take most people an extra 30 seconds of game time to get the result. I don't know about you, but I get bored when people take a lot of time to calculate a damage total.
Empowering the total also removes variability between results. For example, a character doing 4D6 with dice results of 2, 2, 4, 6 does 21 points of damage using empower every die. A character doing the same 14 points on 4D6 with results of 1, 3, 5, 5 does 19 points of damage using empower every die.