This would depend on the area being covered.
The GO4 & GO6 are both capable of covering an area of up to 500 ft2/speaker.
The GO6 of course would be able to cover the area at a greater volume (SPL) than the GO4.
The goal is to have even coverage.
Start by calculating the total square footage of the area and then divide that by 500.
This will provide you with a rough estimate on how many speakers you will require.
Please note that as with all speakers if you wish to have a higher overall volume, divide the area to be covered by a figure less than 500.
Area to be covered 4000 ft2.
4000 ft2 ÷ 500 ft2/sub (GO4 or GO6) = 8
For an area spanning 4000 ft2 you would require 8 GO4s or 8 GO6s
Using 8 GO6s would be perfectly fine as you would have the same coverage with higher volume capabilities.