The best thing to do.....in my personal opiinion only.....is to buy an mh conversion bulb for your hps ballast and use that during veg. Flouros WILL be cheaper but I personally have not been happy with them for vegging my plants. It will be more expensive to go with hps AND flouros but mh lighting is PERFECT for vegging and your plants will thank you by growing bigger and better for it with just one ballast.