2 250W lights would grow the plants, but to get the most out of them I would recommend as much light as you can get. Cannabis does better and better the more light you give it (up to saturation point, but that is higher than most HIDs can provide). The limiting factor with most HID setups is heat. Make sure to vent well and get a fan that you think might be just a little too powerful. For 8 good sized plants, I would recommend either a 1000W HPS with a light mover or two 400W HPS. That way you can provide enough light for optimal results. You could grow 8 plants to a smaller size (3-4 feet) using 2 250W lights, but if you have the space and the money... Use more power! HA HA HA!
Also, I have grown Super Silver Haze(father of Super Lemon Haze) and it seems to need higher levels of light to do well, as most haze varieties do.