I too have a Pete light box, about my third or fourth he has made for me over the years and telescopes.
Get the dimmer as you will find you can fine tune your setup to do LRGB at a lower setting to Narrowband so you can keep above your shutter speed if your camera has one.
LRGB for me is about 7 -20 seconds (red is always longer for me) at about half setting and narrow band about 20 - 30 seconds on flat out.
