Just get a 14,000btu Koldfront online and be done with it. Unless you are going to use Co2. In which case you should just get a 14,000btu window unit. That will cover you up to 4000 watt room roughly
a 14000 BTU unit will have to work overtime to run a truly sealed room in AZ with 4k watts. The math calculations used by an HVAC technician are roughly follows (these are ripped off a farmer from a different forum when I asked him the same question):
SQ. FT of exterior walls and attic walls * 40 BTU = BTU used to cool the room from outside heat sources
+
40 BTU * sq ft of area (based on standard 8 foot cielings) = BTU used to cool the air already in the room
+
3750 * Number of lights (non cooled lights) = BTU used for electronics of lights
Any other electronics you might run in the room (dehumidifier, chillers etc) all have BTU ratings that will need to be added into the equation as well. In the case of my room 4k Watts required a 24K Btu Minisplit unit to properly cool down in the summer months efficiently. (2 exterior walls and an attic above me)
The most efficient A/C you can possibly get for going sealed is a Minisplit with inverter technology.
You will want to make sure your unit is the right size, to prevent it from constantly working, and to prevent it from short cycling in the case that it is too big for the area it is cooling.