Possible?

[stinkyattic]

Is it possible to achieve 1 pd off of 600 watts?

Yes, given enough time in which to do it.

What is a more realistic number with pretty decent growing skills?

Between 0.2 and 0.4 grams per watt per month spent in flower.

Im thinking SOG with Granddaddy purps X moonshine X urkle.

Choose a better yielding strain. The 'elites' were bred for taste/color/effect, not for yield. You want weight, grow a commercial strain.