Im not a theorist in music, but as i understand you can make a power chord by using the root not (say G) and the relative 5th (which would be D) Possibly you can add the 4th, instead. I'm out of my depth here really :)

To get the relative notes you'd count the root as 1 which is
G (say) and would go like this.

G=1
A=2
B=3
C=4
D=5
E=6
F=7

You could use this in any key; ie if A=1 then E=5. This is another one of my halfc_ocked theoeries, so take it with a pinch of salt (seems to work for me) .

..anyone else.. please..