To get a pound a month with a 600W, you'd need to be doing a harvest every month, since a pound or a few ounces over is about what you could expect per harvest. That means you'd need at least two 4x4 flowering spaces with two 600W lights, since most strains need at least two months in the flowering stage, and each 600W needs 4x4 to itself.
It depends on how many plants you want to grow but you'd probably want at least 4 per tent. So you'd need enough space in the vegetative chamber to grow 4 plants that are almost 2 feet tall and would fit a 4x4 (so you can transfer them directly to the flowering chamber and flip to 12/12 immediately), plus room for 4 plants that are about half that size (so they get big enough in time for their turn).
With a 1000W you can expect 2+ pounds on a good grow. So you could have one harvest every 2 months to achieve a pound per month, and only have to maintain one set of vegetative and flowering plants at a time. But it's very important to keep the space cool when you're using a really powerful grow light like that!