Okay, the installation is....done!
I finally pieced together enough info from you guys here, and it's installed the way I want it. I used that Add-A-Circuit plug into the Seat Heater slot (which my SE doesn't have) and the LED lights work only when the key is turned. At some point, I may get motivated enough to take some pics and post a little mini-guide for those who are as clueless as I was.
As for the lights themselves, they're nice and bright. The effect is much more pronounced when pulled up and facing objects (house, trees, whatever). Of course, this applies to any lights, really. I won't be using them as "driving lights." I might also upgrade to some higher wattage/lumens at some point, now that the wiring is in place.