If done correctly, training, fimming, LST'ing super cropping, topping, trimming, etc., Yes it is very possible to achieve 1LB per 600 watt bulb. I know peeps who consistently hit 1 gram per watt. I average 450-550 grams per 600 watt bulb. Also, you need to factor genetics of the strain into the equation. I've never grown SD or Headband before so I can't tell you.
Is this your first hydro grow?
how many plants do u have under that 600?