Most "local stereo shops" are a bunch of worthless hacks from what I've seen. I've spent too much time re-wiring ****ty audio and remote start installs to ever trust them.

During initial startup is when the ballasts draw the most current, but only for about 10 seconds. You might consider installing a relay power harness to supply the ballasts with power directly to the battery.

I have a wiring diagram on my web site below...