Need Help with Lighting in Changing My New Grow Room

I have my grow setup in a spare bedroom. The room is 12x10 and 8 foot high. Right now I have one 600 watt light, a 475 vfm vortex exhaust fan hooked to a 1040 carbon filter. I have plywood down were i sit my plant and have 4 foot wall inclosing it. Its deminsions are 4x6. I want to add another light and don't know if I should go with 2 600 or just 1 1000w. Or do you think the 1 600 and 1 1000 would be ok? I will also be getting a 12000 btu ac to put in there in the next week or so. My grow usually consist on 6 plant in 5 gal buckets. I usually grow them to about 5th from the floor or 4 actual plant height, this is finished height. I want to be able to add another 3 plants to the grow for a total of 9 plants. Given these circumstances what do you all think would be my best lighting setup? Thanks for any input.

With the AC and given electricity cost doen't compare to weight gain I'd say 2 x 1k in that space.