Congrats on the new tank! I have the Aqualight Pro HQI/Compact Fluorescent/Lunar Light Fixture
and love it. I have the 72" 834W on my 125. This fixture includes the 10000°K
HQI double-ended metal halide, actinic blue compact fluorescent, and 1 watt Lunar Blue-Moon-Glow LEDs.
Skimmers, I don't use but Remora is a good name.
The sump can be any size that you can fit under the tank. Remember, the more water volume the better.
I am going to move this to the General Hardware/Equipment section.