I have a similar rig with 3x7950's that pulls right at 1kw. Im working on filling out my variables as I am able to post them but would love to see other's numbers as well. If you have another rig/setup/experience with the same numbers, please post them here so we can see how our numbers stack up!
https://docs.google.com/a/fauls.com/spreadsheet/ccc?key=0AlLhCKa2xFT9dHFlSHprOWx4b0VNeDB3eUM2ZF9BNXc#gid=0