A minimum BTU per square foot for cooling is 20 BTU's. Using your number supplied a 5,000 BTU unit gives you 50BTU per square foot. The 20 BTU is a minimum but then again that represents a "normal room" temperature or 78 degrees. Remember it takes 1 BTU per sqft to heat it 1 degree up (there's another 100 BTU's needed per 1 degree) and therefore it's 1 BTU per sqft to cool it down above the normal 78 degrees. With the lighting system your room reads 90 degrees that's 12 degrees requiring another 1200 BTU's for minimal cooling. This doesn't take into account the condition or insulation of the room in question. Per Energy Star requirements by the DOE; a 100-150 sqft room needs 5,000 BTU normally but what is normal. If your room is on the south or west facing you have to up the BTU's by 10%. If your room is under a canopy of shade trees you can cut 10%. The standard for normal (average) is a house that is 25 years old meeting 25 year old code in insulation! If the room is normally occupied by two people add another 600 BTU. If the room is next to a kitchen where the oven is used add another 4,000 BTU's. Overall, not knowing the age, condition, sun/shade/direction facing of the room but with the lights you are using I'd pick up a 7,000-8,000 BTU unit. 10,000 would be a little overkill. That moves the cost from $169 (5000 BTU) to the $219 range (7000-8000 BTU's). Running your light cycle at night means it should be cooler than the day but if you're in Arizona that means instead of it being 105 it's only 88! But it's a dry heat!