2x600w vs 1000w light mover

Hey my flower space is about 3ftx6ft I currently have a 600w HPS width magnetic ballast on a light mover. I'm thinking to up the ante but not sure which way to go.

I know the 2x600w has more umph but I'm also concerned about heat, I'm currently using a 400cfm fan to vent out the tube. Which setup will create more heat?

I also worried about power draw. So which setup will use less power? I know 600w is "the most efficient" bulb but considering how I have magnetic ballast, if I get a digital ballast will that combo use less than a 1000w dig I ballast?

Also is 1200w overkill for my fairly small and rectangular space that doesn't have the best ventilation, or is a 1000w on a mover fairly comparable?

I guess if you felt you really needed an upgrade go with the 1000 and a digital ballast then you have the option of being in econo mode 600, or when you feel like you need to ramp it up in flower you can dial it up, you got the light mover so I wouldn't think you would get hot spots.But really I think you already got it covered with what you got,Why more?

Frankly, being only three feet wide, I'd just stick with a single 1000. It's far more than enough for that space.