I see a big problem with these in a 4x4x3 area. If you go with a 600 or 1k for a 4x4 area you are going to need a super wide hood (like a 4x4 hood) in order to illuminate the entire area. A small hood from 1 ft away will beam a 2x2 foot plan and surly fry all of your plants in minutes. Even if you get a 4x4' hood the plants will still be right up again the hood and burn - .5' pots + 1.5ft plants and the hoods take up about a foot in height - everything will be touching. In my 4x4x6' tent I have a hard time keeping my light far enough from my mature plants.You could hang a cool tube (requires less height than a hood) but even then I'm pretty sure 1k would fry everything in there and possible a 600 as well. You could try a few 250's in cool tubes and that might work or go with a CFL scrog. With the close proximity you are talking about CFLs can offer equivalent lumens (remember lumes diminish by 4 fold per foot traveled - 1200 lumens from 1" away is 1200 lumens, 5k lumens from 1ft away is 1250 lumens). I grew in a very similar sized enclosure and had great success with a CFL scrog (even with CFLs heat can be an issue).