12v illuminators very close to each other? You'd be better off to run 110v out near them, plug in one 6a wart, and then split to each one. Otherwise, to be under a 5% voltage drop, my math shows a 6a 12v wart and then 150' of 4ga wire out to near the illuminators and then split it. You could get a variable voltage wart and bump up the voltage to compensate for the drop, or say pick a 16v wart and run the numbers to get the right gauge to arrive at 12v. When I plug 16v and 25% voltage drop into a 150' run with 6a at the end into a voltage calculator it tells me 12ga wire with a 20a rated capacity.
Try your numbers here-
Voltage Drop Calculator