This is a very vague 2 part question. There is no magic number that you stay below and the feds don't come knocking. 6k watts is not an obscene amount of power if you setup your room efficiently. As far as growing more than your legal limits all I can say is don't be stupid. California has pretty awesome medical marijuana laws by abusing them you ruin it for the rest of us and subject yourself to Jailtime, fines, probation, thousands of $ in lawyer fees etc. It my city I am allowed 5 lbs. of herb and 99 plants. Do you really need to harvest more than that? If you are planning on moving out here, renting a house and trying to grow 1000 plants please just stay where you are at, don't ruin it for everyone man.