Clarification please. This "second wire for the power"....I think you are talking about the control side of the circuit, correct? Sometimes people will wire this into the high beam circuit so that the aux. lights come on with the high beams. I have no idea why......
But, you should have 2 +12v circuits. One, the Load circuit, which starts at the battery, or better yet, a fuse block fed off of the battery, goes through the load side of a relay, and ends at your lights (which are then grounded to either the chassis, or back to the battery).
The other +12v circuit, the "control" circuit is what opens and closes the contacts of the relay. This is the one that some people wire into the hi beam circuit. You can get source voltage anywhere you want for this, but would be wise to take it from a circuit that is not extremely voltage sensative. Take it from, say, the battery side of the headlight circuit (pre-headlight switch), not from the circuit powering your ECM.
Below is a diagram I stole from the net...the wire they have going to the on/off switch is the control circuit (what I think you are referring to)--get that power from wherever you want...just remember that if you don't take it from a switched source (one that loses power when you turn the ignition switch off), it is possible to have the lights on with the engine off--which will drain your battery if you forget to turn them off.
