How much of an area can a 400 watt HPS bulb cover?

How much of an area can a 400 watt HPS bulb cover? I'm thinking about ordering this bulb since it also has 30 watts of blue light:
http://www.specialty-lights.com/9960.html

also I'm thinking about throwing in some CFL's to add to the lighting. Is this a good idea?

3'x3' , IMO

I guess you have a ballast already..they say up to a 4 by 4 area...have mine in a 3 by 3...

3x3 ..............

thanks for the info everyone! If I were to add in some CFL's could I expand the 3x3 ft area to say a 4X4 ft area? or maybe more?

50 watts minimum per SQ Ft. The more Lumens & Watts per SQ FT the higher the yield usually.

you could do that but why??? why not just get a bigger light?? 400w not enough then dont add CFLS just get a light thats big enough for 4x4......go the simple most efficent way......

4x4=100w 3.5x3.5=600w 3x3=400w so just get yourself a 1000w or atleast a 600w and be DONE...your yield will be better then if you use a 400w and sub in cfls too.......

yeah 3x3 is right on, I have a 400w in a 4x4 tent, its only used for veg, but if I were to flower in there it would not be enough, the light doesn't penetrate well and is weak at the edges of the garden. 600w is fine for a 4x4 imo.