Looks like you have a pretty good list of parts there, but I do have a question for you. What kind of wire splices did you get?
The preferred way to wire up the lights would be to solder/heat shrink it.
The next best way is to go with waterproof butt connectors. These are sometimes called heat shrink butt connectors.
The weatherpack connector that Jason mentioned is an excellent option as well.
The reason I mention it because the standard butt connectors that Home Depot and Radio Shack sell are not waterproof. Most of the auxiliary lights that I have seen have a pretty short (usually ~6 inches) wire lead on the back of them. Since you are mounting your lights on your bumper, this means that your splice will be very near your bumper. Things like standard driving in the rain or driving through a puddle/stream on the trail will send a lot of water to the area of your splice. So you really want a good waterproof connection on those splices.
Just food for thought...
In case you are curious, this is how I did my splices for the lights on my bumper and roof. (sorry for the crappy cell phone pics...)
Solder it (make sure the heat shrink is on the wire before you solder)

Then slide the heat shrink over the solder and heat it
