Yield will depend on too many things for anyone to really predict with any accuracy. Are you going to flower with ALL your lights? How long are you vegging for? Have you pruned for yield (to generate more bud sites)? Strain, temps, nutes, just too many variables. The holy grail is 1 gram/watt/crop, or 0.5 grams/watt/month. So if you flower with both 400 watt MHs and the 600 watt HPS, you could theoretically yield 1400 grams, if everything goes perfectly. In reality, aim for half of that (1.3 pounds or so if you use all the lights) and be happy if you get it. If you just use the 600 watt light to flower, be happy with 10 ounces or so and consider anything beyond that a bonus for a job well done. Better to be a pessimist and happily surprised than an optimist and bitterly disappointed.