How much A/C?

I'm running 1,600W home-made cob fixtures and a veg tent with about 400W of Samsung strips, plus the usual fans and pumps etc. I'm assuming an absolute max wattage of 2.4Kw on a 240v system, so about 10A of total draw. all in the same room.
If I further assume a completely sealed and insulated room of 3x6x3 metres (for the colonials, that's about 10x20x10 feet), how much air conditioning will I need?
I'm hoping that a modern 2.5Kw unit (0.7108628402 tons of refrigeration) will be ok.
Has anyone any good experience that would be helpful?
(yes, I'm planning to add dehuey and co2, when I get the split installed)

Take the total watts going into the room (all of it, fans, dehu, lights, pumps... Total watts X 3.41 = BTU/hr generated. This is easy with LED, HPS is more difficult due to the amount of IR wavelength.

2400 watts x 3.41 = 8184 BTU/hr

My room is about same size as yours, mine is 2.9m wide, 4.5m long and 2.9m tall. (3x4.5x3m) I run around 4000w of light and 3 dehums and my 5.2kw aircon barely keeps up. My room is very well insulated and completely sealed. I have to dim some of my lights to keep the room at 30 - 31c

If you are down under like your name suggests I would go a 7.2kw if you want to jam pack that area. I regret not going bigger.

Thanks for the responses guys - it seems that it's exactly as I suspected, the amount of watts going in has to be matched by the amount of a/c. Stands to reason really.
I think I'll have problems with a bigger a/c (noise etc), so I'll have to keep my power usage at its current level.
Thanks again and good luck.